The 145th (2021 FALL) SEGJ CONFERENCE

Nov. 24 Room No.1 (Conference Room 61, 6F)

Session	[Oil and Natural Gas][Groundwater][Resource Exploration 1]
Chair	Tada-nori Goto (University of Hyogo)

Nov. 24	10:00 - 10:20　　　 We conducted "high-resolution 3-dementional image mapping" in Shallow Methane Hydrate (MH) distribution area off Sakata, Yamagata Prefecture on the eastern margin of the Sea of Japan, for the purpose of detail optical observation of the seafloor. A continuous 3D image of seafloor has acquired by laser scanning and still images of seafloor using ROV-Kaiyo3000 and a system named “SeaXerocks1”. Detail topography data and still image are combined to create the pictorial image with the topographical change, color information, and location information of the seafloor. Our observation revealed that outcrops and bacterial mats, which are considered to be related to methane gas seepage, frequently occur inside the depression at the summit area of the Sakata Knoll. The distribution of outcrops and bacterial mats partly overlap. The distribution of outcrops is wider than that of bacterial mats. The distribution of bacterial mats suggests the areas of present-day limited methane seep, while the outcrops can indicate the extent areas of methane seep including the past and have been preserved to date.	1) Investigation of the seafloor condition in the shallow methane hydrate field off Sakata, eastern margin of the Sea of Japan
Nov. 24		*Asada Miho・Satoh Mikio(1) 1:AIST
Nov. 24	10:20 - 10:40　　　 We implemented the generation of pre-stack data based on Multi-dip Reflection Surfaces (MDRS) method which is capable of solving the conflicting-dip problem. It also inherits the features of the family of Common Reflection Surface methods: extremely high S/N production and minimal degradation of lateral resolution while stacking plurality of neighboring CMP traces. The real data example shows that the implementation achieves high S/N of generated data and effectively complements missing offsets. These benefit the quality of subsurface images of PSTM processing combined with MDRS pre-stack data generation.	2) High S/N pre-stack data generation by Multi-dip CRS (MDRS) method
Nov. 24		*Shogo Narahara・Hidehiko Shimizu(1),Hiroshi Sato(2,3),Tatsuya Ishiyama(2),Kenichi Akama(4) 1:JGI,2:Univ. of Tokyo,3:Shizuoka Univ.,4:JAPEX
Nov. 24	10:40 - 11:00　　　 Both fluid production from oil and gas reservoirs and injection into underground for EOR, hydraulic fracturing and CO2 storage may cause formation deformation or failure. Geomechanics for predicting and controlling the rock deformation and failure will attract further attention with the increased interest in CCS as one of the expected carbon-neutral technologies. A workflow of recent geomechanics study based on a geomechanical model has been established. However, all the data required for geomechanical modeling are not always available at actual operation fields. We expect rock physics to provide supplemental information useful for geomechanics and conducted this study to demonstrate with field data. Comparison of the data with rock physics models indicated the slight decrease in P-wave velocity due to gas effect and fluid substitution was conducted to predict the velocity when saturated with water. Geomechancal models were constructed respectively with the raw and corrected data and compared for the effect on sanding evaluation. We hope this preliminary study will further strengthen the link between rock physics and geomechanics.	3) Practical Geomechanical modeling of Oil and Gas Fields and Rock Physics
Nov. 24		*Koji Kashihara・Yu Uchida・Kyohei Inoue(1) 1:JAPEX
Nov. 24	11:00 - 11:20　　　 Recently, lunar development has been accelerated, and the acquisition of the ice on the Moon has attracted attention. However, the distribution and amount of the ice are still unclear. Understanding the relationship between ice saturation and elastic wave velocity enables us to estimate its amount from seismic data. To clarify the relationship, we numerically calculated S-wave velocity by changing ice size, distribution, and saturation from digital image data of regolith simulant. The Quartet Structure Gene ration Set (QSGS) was used to add ice within the digital model. The result demonstrates that the characteristics of velocity change with increasing ice saturation is different depending on the ice features. The simulated result is closest to the experiment result when the larger ice clusters are distributed in the model. This research shows that the ice distribution within the pore space can be determined from the relationship between elastic wave velocity and ice content.	4) Relationship between ice saturation and S wave velocity of lunar regolith simulant based on digital rock physics and experiment
Nov. 24		*Takaaki KUNIMASU・Kazuki SAWAYAMA・Tatsunori IKEDA・Takeshi TSUJI(1) 1:Kyushu University
Nov. 24	11:20 - 11:40　　　 Deep learning is a machine learning method that has been attracting attention in various fields and has achieved great results, for example, in the field of natural language processing and image recognition. In this study, we set the advantages of EM inversion using deep learning as (1) inversion can be performed without the need for an initial model, (2) high-speed calculation of a large amount of observed data. We have developed and applied the inverse analysis using deep neural network (DNN) to the frequency domain airborne electromagnetic system (RESOLVE). Matsumoto and Ueda (2021) confirmed the validity of the deep learning methods with synthetic data. The results of the deep learning inversion showed good agreement with those of the existing method. However, the algorithm to generate the supervised data and the composition of explanatory variables were considered insufficient to bring out the power of DNN. Therefore, we reviewed the way of supervised data and tried to improve the performance of DNN by adding features and Gaussian noise. As a result, the results are more stable than Matsumoto and Ueda (2021) model and more harmonious with the results of 1D inverse analysis using the Gauss-Newton method.	5) Upgraded Deep Neural Network Inversion of Frequency-Domain Airborne Electromagnetic Survey Data
Nov. 24		*Tamaki Nishino・Takumi Ueda(1) 1:Waseda University


Session	[Structure][Bedrock][Civil Engineering 1]
Chair	Kosuke Chimoto (Kagawa University)

Nov. 24	13:00 - 13:20　　　 The noncontact acoustic inspection method using acoustic irradiation induced vibration and laser Doppler vibrometer can detect internal defects in concrete from a long distance, and verification experiments have already been conducted in various places. However, the conventional measurement surface has been performed on a surface having relatively few irregularities. Therefore, this time, an application experiment was conducted on shotcrete in the ceiling of a large underground cavity. From the experimental results, it was clarified that even on a shotcrete surface with irregularities, defective parts can be detected from a long distance of about 25 m, which is similar to that of a hammer inspection.	6) Research on noncontact acoustic inspection method for non-destructive inspection, -Application to shotcrete surface of large underground cavern ceiling-
Nov. 24		*Tsuneyoshi Sugimoto・Kazuko Sugimoto(1),Hiroshi Morioka(2),Noriyuki Utagawa(3) 1:Graduate School of Engineering, Toin Univ. of Yokohama,2:Tokyo Electric Power Company Holdings,3:Technical Research Institute, SatoKogyo Co., Ltd.
Nov. 24	13:20 - 13:40　　　 It is required to establish a method for inspecting concrete quality by the non-destructive testing methods to maintain concrete structures such as underground foundations, maintenance holes and so on. Seismic velocity and electrical resistivity vary with compressive strength or water saturation, so there is a possibility to evaluate concrete quality by these parameters. In this study, the authors conducted laboratory measurements of uniaxial compressive strength, P-, S-wave velocity and electrical resistivity of concrete specimens in various composition and water saturation conditions. The results demonstrated that a positive correlation was observed between P-, S-wave velocity and uniaxial compressive strength, and a negative correlation was observed between electrical resistivity and water saturation, respectively.	7) Study on elastic wave velocity and electrical resistivity of concretes
Nov. 24		*Kenji Kubota・Yohei Morifuji・Taku Otsuka・Toshinori Kanemitsu(1) 1:CRIEPI
Nov. 24	13:40 - 14:00　　　 In the concrete dam, cracks are easy to occur on the surface of the concrete along the joints of the concrete. Therefore early detection and evaluation of cracks are necessary. The depth of cracks in concrete has been estimated using the attenuation of surface waves (Rayleigh waves). This method uses an empirical equation derived from experiments on soft ground, but it also gives good results for hard materials such as concrete. This is because one hypothesis is that the degree of damping caused by cracks is expressed as the ratio of the total energy to the energy at the depth of the crack. In this paper, this hypothesis is verified by experimental results and theoretical calculations, and is found to be correct.	8) Estimation of crack depth in concrete using attenuation effect of surface wave
Nov. 24		*Yoshiki Minami・Hiroyuki Azuma・Yoshiya Oda(1),Toru Takahashi(2),Kyosuke Onishi(3),Shinichiro Iso(2) 1:Tokyo Metropolitan University,2:Fukada Geological Institute,3:Public Works Research Institute
Nov. 24	14:00 - 14:20　　　 It is necessary to understand distribution of hydraulic permeability of bedrock in the deep underground. In this study, we aim to construct a rock physics model for estimating the permeability of fractured granite using integrated geophysical exploration. Our proposal is based on two-step models: a matrix model with small inclusions (i.e., microscopic fractures), and a bulk rock model with larger inclusions (i.e., macroscopic fractures). We first apply our matrix model to the rock mass without macroscopic fractures, then apply the bulk rock model to the fractured granite. The theoretical values of the seismic velocity and resistivity are calculated by using the equations for two-phase media and the modified Archie's equation, respectively. The permeability can be estimated from the parameters in the modified Archie's equation. Based on the field geophysical data, we confirmed the validation of our rock physics model. The rock physics model for seismic velocity and resistivity was constructed based on logging data obtained at the Toki granite area, Gifu prefecture. The predicted fracture porosity and bulk permeability are compared with the measured values. As a result, both predicted values showed good agreement with the measured ones, which indicated the validity of our rock physics model.	9) Proposal of rock physics model for seismic velocity, resistivity, and permeability of fractured rock
Nov. 24		*Tada-nori Goto(1),Sota Kawaguchi(2),Yusuke Ozaki(3),Yusuke Ohta(4),Taiki Kubo・Koki. Kashiwaya・Katsuaki Koike(5) 1:Univ. Hyogo,2:CFK,3:JAEA,4:Nagoya Univ.,5:Kyoto Univ.
Nov. 24	14:20 - 14:40　　　 Reflection seismic survey is generally used for evaluation focusing on the geological boundary of sediments and the upper surface of bedrock. On the other hand, there are few cases of evaluation of hard rock. Therefore, in this study, we tried to compare the reflection seismic survey, elastic wave tomography using two boring holes, and PS logging carried out at a hard rock site. Comparing the reflection seismic survey data and the tomography’s ones, their shape and depth of the velocity structures were almost same. In addition, comparing the reflection seismic survey data and PS logging data, slight velocity differences was observed near the reflection surface. Based on the geological data, it is suggested that this reflection surface may have been formed by the velocity difference due to the slight difference in the rock hardness and the number of rock cracks.	10) Comparison between reflection seismic survey and another survey methods at a hard rock site.
Nov. 24		*Shingo Hisaoka・Hirotoshi Akira(1),Koji Yamada(2),Akiyuki Iwamori(1),Daiei Inoue(3) 1:KEPCO,2:Hanshin Consultants,3:CRIEPI


Nov. 24 Room No.2 (Conference Room 63, 6F)

Session	[Geothermal][Volcano]
Chair	Daisuke Ohara (Nippon Koei Co., Ltd.)

Nov. 24	13:00 - 13:20　　　 We carried out DAS seismic measurements at the Mori geothermal district. The optical fiber was placed down to 2,100 m depth. We excited medium size IVI vibrator at eight source locations. The DAS data were stacked for 480 times. We applied the F-K filter to separate upgoing and down-going phases in the DAS records. We can identify several reflected phases and the gap of first arrival travel time at 1,060 m depth. We carried out the Vp travel-time tomography along the EW and NS profiles. Using the Vp 2D distribution, we calculated synthetic DAS record. The travel time gap is not well reproduced.	25) DAS-seismic study at Nigorigawa district, in Mori town Hokkaido, Japan
Nov. 24		*Junzo Kasahara・Yoko Hasada・Hiroshi Ohnuma・Haruyasu Kuzume(1),Hitoshi Mikada(2) 1:ENAA,2:Kyoto University
Nov. 24	13:20 - 13:40　　　 In geothermal development, it is important to understand the complex subsurface structure near wells and the behavior of fluid flows. In this study, microseismic events were monitored at two sites, Site A and Site B, in order to understand the structure and fluid flows near the well. In Site A, the power plant was halted twice for the purpose of periodic inspection during the microseismic monitoring, and several wells were operated (stopped / restarted) regarding the inspection. In Site B, production tests were conducted three times during the microseismic monitoring. We focused on the microseismic events that occurred regarding these production tests. The number of microseismic events in Site A during the entire period was highest for microseismic events with a local magnitude (M) range of -1.5 to -0.5. This tendency was not changed dramatically during the periodic inspections. However, focal depths of the microseismic events during those periods became deeper. In Site B, clear increase in intensity of microseismicity was not observed regarding the production tests, nor occurred large earthquakes with the local magnitude (M ≧ 2).	26) Structure survey around geothermal wells based on microseismic exploration: part 1
Nov. 24		*Yuki Tanaka・Kyosuke Okamoto・Hiroshi Asanuma(1),Naoshi Aoki(2),Kazumi Osato(3),Shinya Onodera(4) 1:AIST,2:JGI, inc.,3:GERD,4:JOGMEC
Nov. 24	13:40 - 14:00　　　 Understanding the fracture system and behavior of geothermal fluid around geothermal wells is indispensable for efficient and sustainable geothermal development. In ordinal, seismic reflection survey has advantage to reveal the information mentioned above. However, repeated and large-scaled surveys are difficult due to cost and steep land restrictions peculiar to geothermal areas. In this study, we focused on a passive exploration method using microseismic events that occur near wells. Two geothermal fields currently under developing are target areas in this study. We conducted microseismic monitoring over more than a year at these fields. We introduce case studies in which reservoir structure and behavior were revealed by the combination of hypocenter determination, focal mechanism analysis, seismic wave tomography.	27) Structure survey around geothermal wells based on microseismic exploration: part 2
Nov. 24		*Kyosuke Okamoto・Yuki Tanaka・Hiroshi Asanuma(1),Naoshi Aoki(2),Kazumi Osato(3),Shinya Onodera(4) 1:AIST,2:JGI,3:GERD,4:JOGMEC
Nov. 24	14:00 - 14:20　　　 It was reported that volcanic activity got active near Hachijojima in 2002. To evaluate the risk of eruption, we will analyze underground structures by a technique using natural earthquakes. Hence, we need many and accurate first arrivals of seismic waves generated by natural earthquakes to improve the accuracy of the analysis. However, the number of earthquakes near Hachijojima is small and it takes much time to identify the first arrivals of seismic waves manually. Therefore, we try to increase the number of detected earthquakes, to automate the identification, and to improve the accuracy of the identification by applying deep learning with Transformer.	28) Automatic Detection of First Arrival Time of Seismic Waves with Deep Learning using Transformer: Applying to Observed Data in Hachijojima
Nov. 24		*Hikaru Kunimasa・Ryohei Tottori・Hiroyuki Azuma・Yoshiya Oda(1) 1:TMU
Nov. 24	14:20 - 14:40　　　 Seismic interferometry is a method of synthesizing a wavefield between two points by calculating the cross-correlation function of seismic wave records observed between two points. To understand the applicability of the seismic interferometry to the data acquired in an island that is surrounded by ocean, we have applied the seismic interferometry to the microtremor data observed by dense micro-earthquake observation in Hachijojima Island in 2019-2020. In addition, since the Typhoon No. 15 passed through the vicinity of Hachijojima Island during the observation period, we applied seismic interferometry to the data before and after the typhoon passed, and compared the results. As the results, we obtained the cross-correlation functions with relatively good symmetry using only seven days data. However, we found that the symmetry is affected by the ocean wave direction and wind direction.	29) Application of seismic interferometry to dense seismic observation data in Hachijojima Island
Nov. 24		*Utako Watanabe・Hiroyuki Azuma・Yoshiya Oda(1),Toshiki Watanabe(2) 1:TMU,2:NU


Nov. 24 Core Time: Room No.1, Exhibition: In front of Room No.1 or Online

Session	[Poster Sessions: Core Time 1]
Chair	Koji Kashihara (JAPEX)

Nov. 24	15:00 - 15:50　　　 Negative apparent resistivity is sometimes observed by the three-dimensional resistivity survey. The negative apparent resistivity should be removed for the dataset because a resistivity inversion generally uses the logarithm of the apparent resistivity as input data. First, a numerical simulation was conducted to understand a cause of the negative apparent resistivity. As a result, it was found that negative apparent resistivity was obtained by the effects of topography and three-dimensional resistivity structure. Next, another numerical simulation was conducted to assess a usability of the vector inversion technique proposed by Loke et al (2019). In this technique, the data which measured in two orthogonal directions are converted to amplitude and direction. Because the amplitude shows always positive value, the logarithm of the amplitude can be used in the inversion process. Therefore, this technique is effective for the data containing negative apparent resistivity. As a result of the simulation, it demonstrated that the vector inversion was robust against noise compared to the traditional inversion technique using individual components.	P-1) Vector inversion of three-dimensional electrical resistivity data
Nov. 24		*Hiroshi Kisanuki・Ken Sakurai(1) 1:OYO
Nov. 24	15:00 - 15:50　　　 Three-dimensional (3D) marine controlled-source electromagnetic (CSEM) surveys have been used to map complex resistivity structures. Typically, these 3D CSEM surveys use dozens of ocean-bottom electric (OBE) receivers and several transmitter towlines. The cost of a 3D CSEM survey largely depends on the number of deployed OBE receivers. Conventional types of 3D marine CSEM surveys use many OBE receivers (> 10 OBE receivers), resulting in high survey costs. However, an economical 3D CSEM survey using fewer OBE receivers has not previously been proposed. Therefore, this study proposes a cost-effective 3D marine CSEM survey that uses fewer receivers than the conventional survey to reduce survey costs. This proposed CSEM survey uses a line of OBE receivers in the center of the survey area and several transmitter towlines. Numerical tests demonstrated that the proposed survey (with 7 OBE receivers) using 80% fewer receivers than a conventional survey (with 35 OBE receivers) was able to accurately map seafloor resistivity structures. This demonstrates a high cost-effectiveness of the proposed survey.	P-2) Efficient three-dimensional marine controlled-source electromagnetic survey
Nov. 24		*Keiichi Ishizu(1),Weerachai Siripunvaraporn(2),Tada-nori Goto(3),Katsuaki Koike(4),Takafumi Kasaya(5),Hisanori Iwamoto(6) 1:Tokyo Tech,2:Mahidol University,3:University of Hyogo,4:Kyoto University,5:JAMSTEC,6:NME
Nov. 24	15:00 - 15:50　　　 Subsurface fluids in a supercritical state (high temperature and pressure of >374°C and >22.1 MPa) have gained attention as next-generation geothermal resources because they can offer significantly more energy than conventional geothermal fluids with temperatures <350°C. Supercritical geothermal fluids are believed to be found in various volcanic areas worldwide. Although an understanding of the spatial distribution and fluid fraction of supercritical fluids is necessary for their resource assessment, the spatial distribution and fluid fraction of supercritical geothermal reservoirs are poorly understood. Therefore, we used the magnetotelluric (MT) method to obtain information on the spatial distribution and fluid fraction of a supercritical geothermal reservoir in the Yuzawa geothermal field, northeastern Japan. Our MT data revealed a potential supercritical geothermal reservoir of 3 km (width) × 5 km (length) at a depth of 2.5-6 km with a fluid fraction estimated to be 0.5-2% and a salinity of 5-10 wt%.	P-3) Estimation of spatial distribution and fluid fraction of a potential supercritical geothermal reservoir by magnetotelluric data: a case study from Yuzawa geothermal field, NE Japan
Nov. 24		*Keiichi Ishizu・Yasuo Ogawa(1),Keishi Nunohara・Noriyoshi Tsuchiya・Masahiro Ichiki(2),Hideaki Hase(3),Wataru Kanda(1),Shinya Sakanaka(4),Yoshimori Honkura・Yuta Hino(1), et al. 1:Tokyo Tech,2:Tohoku University,3:GERD,4:Akita University
Nov. 24	15:00 - 15:50　　　 The applicability of surface wave tomography using ambient noises was investigated in the Kuju geothermal area to efficiently determine the location of geothermal reservoirs. The surface waves were extracted from the cross-correlation of long-term ambient noises data, and the 3D S-wave velocity structure was estimated by surface wave tomography based on the dispersion curve estimated by the zero-crossing method. As a result, low-velocity anomalies, which may reflect fracture zones related to geothermal reservoirs, were identified. To investigate the advantages of our approach, the estimated S-wave velocity structure is compared with previous studies using natural earthquakes. The comparison show that, compared to the previous study using natural earthquakes, the surface wave tomography using ambient noise has higher resolution in the shallow depth direction, although the horizontal resolution is lower due to the lower density of seismometers. We conclude that ambient noise survey is useful in exploration in geothermal areas.	P-4) 3D S-wave velocity structure in geothermal fields using ambient noise surface wave　tomography
Nov. 24		*Takeru Aramaki・Tatsunori Ikeda・Takeshi Tsuji(1),Yuki Yamaura(2) 1:Kyushu University ,2:WJEC
Nov. 24	15:00 - 15:50　　　 There are many pores and cracks in the underground rock. Moreover, some of them are hydraulically interconnected and others are disconnected; besides, some properties of the fractures are frequency dependent, meaning that seismic exploration has the potential to become a good tool to characterize underground rocks. However, the physical explanations are insufficient, which limits application of seismic exploration. Seismic waves propagation could cause the deformation of cracks and fluid will flow in hydraulically interconnected cracks. Therefore, it is necessary to build a model to study fluid flow caused by the wave propagation for the reason that fluid flow causes energy loss which leads to the wave attenuation and velocity dispersion. We build a numerical model to simulate the wave-induced fluid flow by applying constitutive relationship and Navier-Stokes equations to describe solid phase and fluid phase, respectively.	P-5) Simulation-based rock physics modeling for wave-induced fluid flow in fractured media
Nov. 24		*WANG Xiaoliang・Jun Matsushima(1),Mohammed Ali・ Fateh Bouchaala(2) 1:University of Tokyo,2:Khalifa University
Nov. 24	15:00 - 15:50　　　 A 3D seismic reflection experiment by simultaneous shooting method was conducted off Numazu in July 2021. In the experiment, we adopted four underwater speakers as a source system and a single streamer cable as a receiver system. The underwater speaker can be one of the non-impulsive seismic sources available in marine and comes into use for seismic surveys in very shallow waters. In this paper, we would like to demonstrate results of wavefield separation and subsequent 3D seismic data, and to discuss about practicality of the underwater speakers to 3D seismic surveys with simultaneous shooting.	P-6) A 3D Marine seismic experiment using non-inpulsive multi-sources
Nov. 24		*Rema Kurosawa・Kazuki Takanaka・Ryo Sudo・Kazuo Amakasu・Tetsuro Tsuru(1) 1:Tokyo University of Marine Science And Technology


Session	[Poster Sessions: Core Time 2]
Chair	Tsutomu Ochiai (Kanagawa University), Kota Koshika (OYO Corporation)

Nov. 24	16:00 - 17:30　　　 InSAR (Interferometric Synthetic Aperture Radar) is a method to analyze the state of the ground surface and its displacement by irradiating it with a SAR (Synthetic Aperture Radar) multiple times and receiving the radar reflected from objects. An earthquake (M 7.2) occurred in the southwestern part of the Republic of Haiti on the August 14, 2021. In order to consider the state of the surface damage and the generation mechanism of this earthquake, we analyzed the crustal movement before and after the earthquake by using the principle of D-InSAR (Differential Interferometric SAR). We used two pairs of ALOS-2 data which consisted of data form ascending and rightward irradiation. From the analyzed SAR interferogram, we can detect the crustal movement in western part of the earthquake source. We can also consider that the Enriquillo-Plantain Garden fault zone (EPGFZ), which crosses the southern part of the Republic of Haiti from east to west, is the key to this earthquake. We speculated that there is a source fault along the EPGFZ in the central part of the interferogram.	P-7) InSAR derived ground motion of 2021 Haiti earthquake
Nov. 24		Taiki Marufuji・Takahisa Tashiro・*Koichi Suzuki(1) 1:Hokkaido University
Nov. 24	16:00 - 17:30　　　 In recent years, extreme weather has caused serious disasters. These areas have been hit by floods caused by typhoons, heavy rain, and sediment-related disasters caused by earthquakes and heavy rainfall. The purpose of this study is to investigate the possibility of extraction and monitoring of ground deformation before and after mainly sediment disasters using interference synthetic aperture radar (InSAR) analysis. Several disaster-affected regions were considered and an analysis was performed on a model area. ALOS-2/PALSAR-2 (level 1.1, polarization: HH, incident angle: 34.3 °) and Sentinel-1A/1B (VV: horizontal polarization and VH: cross polarization) were used.	P-8) Utilization of Interferometric Synthetic Aperture Radar Technology for Disaster Prevention and Mitigation
Nov. 24		*Takako Nakamura・Jun Matsushima(1),Shuichi Rokugawa(2) 1:The Univ. of Tokyo,2:NIED
Nov. 24	16:00 - 17:30　　　 We developed a database of geophysical investigation results particularly for S-wave velocity (Vs) profiles, dispersion curves or horizontal to vertical spectral ratios (H/V) obtained from single station three component microtremor measurements, microtremor array measurements (MAM), or surface wave measurements. Our database is open to the public and users can upload their measurement results and share them with community through internet. The system consists of autonomous seismographs and processing software on mobile devices so that users can easily measure ambient noises, calculate Vs profiles and/or H/V and upload the results to the database. The database is integrated with other public databases and users can process and interpret geophysical data together with shallow to deep subsurface information in the other databases. We measured H/V and Vs profiles approximately 3400 and 1200 sites respectively and opened to the public. This paper introduces the outline of the database and dense H/V measurements at Kanto Plain as an application example.	P-9) Autonomous and voluntary geophysical database - Dense H/V measurements at Kanto Plain -
Nov. 24		*Koichi Hayashi(1),Toru Suzuki(2),Chisato Konishi・Hisanori Matsuyama・Haruhiko Suzuki(1) 1:OYO Corporation,2:Mony Exploration Corporation
Nov. 24	16:00 - 17:30　　　 I performed the dense microtremor measurements in the Fukuyama Plain, and estimated the shallow underground structure by using the predominant frequency and H/V spectral ratio. The surface layer thickness gradually increases to the southeast of the plain, while the S-wave velocities in the surface layer were obtained to be around 350 m/s at every sites. The Fukuyama Plain had been created by the reclamation projects since the Edo era. Before that, it was the ocean area with the mouth of the former Ashida River in the northwest of the present plain. The spatial distribution of the surface layer thickness shows that the river sediment had formed a fan-shaped pattern of the shallow sea floor. However, the surface layer in a part of the plain is extremely thin compared with the adjacent area. This suggests the existence of the former reef areas.	P-10) The old seafloor topography beneath Fukuyama plain estimated by using the microtremor measurements
Nov. 24		*Atsushi Mukai(1) 1:Fukuyama City Univ.
Nov. 24	16:00 - 17:30　　　 We conducted a high-resolution S-wave seismic reflection survey for delineating near surface structure beneath a coastal plain facing Ensyunada Sea, in Kakegawa City, Shizuoka Prefecture. S-wave downhole survey was appended to clarify the S-wave velocity structure up to 30 m in depth. We utilized the Landstreamer which consisted of 96-channel horizontal geophone array at 50 cm intervals. A slim-hole type borehole probe was deployed for the downhole S-wave measurements. Horizontal hitting of wooden plank was employed to generate a polarized SH-wave impulsive signal for both surveys. Finally, we created migrated depth sections along the survey lines based on the near surface S-wave velocity structure reconstructed from downhole S-wave measurement data. A clear event was delineated at about 20 m in depth. The reflector showed flat structure beneath the coastal side, and gradually ascended towards the hill side. In addition, it formed a small, buried valley near the foot of the hills. Lithofacies and S-wave velocity profiles of two check borings, drilled near the buried valley, were concordant with the seismic depth section.	P-11) Imaging of near surface structure beneath a coastal plain utilizing Landstreamer S-wave reflection survey and downhole S-wave measurements
Nov. 24		*INAZAKI Tomio(1),MATTA Nobuhisa(2),KAGOHARA Kyoko(3),OKADA Shinsuke(4),NAKANISHI Toshimichi(5),HORI Kazuaki(6),NAKANO Takayuki(7) 1:AIST,2:Okayama Univ.,3:Yamaguchi Univ.,4:Iwate Univ.,5:Fujimu,6:Tohoku Univ.,7:GSI
Nov. 24	16:00 - 17:30　　　 The author had conducted high-resolution seismic reflection surveys from 2003 to 2006 in Tokyo Lowland and in Nakagawa Lowland areas. The surveys were implemented as a part of the comprehensive research of the Chuseki-so in the Tokyo metropolitan area promoted by AIST. The seismic surveys were conducted along 8 survey lines. Total length of the survey lines amounted to 10 km. Among them, the author had interpreted the processed depth sections of 5 lines. Regretfully the remaining 3 lines have not been published. S-wave type Land Streamer developed by the author was utilized to the surveys conducted at densely populated residential districts in Tokyo Lowland. A mini-streamer was adopted for the survey, line of which was set in the stream of Nakagawa. The author re-processed the dataset and successfully imaged the basement and internal structure of Chuseki-so beneath the survey lines. High-performance and low-cost seismic processing software running on windows PC enabled us to re-process even legacy near surface geophysical data and to re-interpret the detailed near-surface geological structure.	P-12) Reprocessing and compilation of legacy high-resolution seismic reflection survey data obtained in Tokyo and Nakagawa Lowland areas.
Nov. 24		*INAZAKI Tomio(1) 1:AIST
Nov. 24	16:00 - 17:30　　　 The previous gravity survey and study show the northern end of the blind active fault in the southern part of the Sendai Plain are located around Masuda in Natori city, Miyagi Pref., which is not connected to the Nigatake blind fault of the Nagamachi-Rifu active fault zone. In this study, to reveal the southern end of the blind active fault in the southern part of the Sendai Plain, we executed four lines of gravity survey across the plain from west to east around the Yamamoto town, Watari county, Miyagi Pref. The result of two lines of our survey line on the north side show the Bouguer gravity anomaly corresponded to the blind active fault. In contrast, the two lines on the south show no significant signal of the Bouguer gravity anomaly which is caused by the blind active fault. These results indicate that the southern end of the blind active fault is located around Takase in Yamamoto town. The blind active fault is considered to be distributed for about 25 km long from the northern part near Masuda, Natori city.	P-13) Southern extension of the blind active fault in the southern part of the Sendai Plain, deduced from Bouguer gravity anomaly
Nov. 24		*Shinsuke Okada(1),Ryota Ambo・Tomomi Okada(2) 1:Iwate Univ.,2:Tohoku Univ.
Nov. 24	16:00 - 17:30　　　 The three-dimensional distributions of lithological properties obtained by usu ally-used property inversion of potential filed quantities can be regarded as eqivalent to the purbations in seismic tomography, and such properties often m akes it difficult to correlate them with actual distribution of geological bod ies. Sun (2015)，Sun and Li (2012, 2016, 2017) suggested a new inversion metho d, into which Fuzzy c-mean (FCM) clustering was introduced as a constraint, so as to enable direct correlation with the actual geological bodies (They calle d such correlation "geological differentiation"). We developed the clustering inversion that introduces Sun's FCM clustering constraint and a uniquely desig ned constraint condition that reinforces it, and have confirmed that our meth od has a potential that the geological differenceation is established, and tha t it has a strong parameter dependence. Here, we present the outlines of clust ering inversion and the results obtained by applying it to the gravity and mag netic data of the Sakata Plain, Yamagata Prefecture.	P-14) Development of clustering inversion of potential field data for geological differentation
Nov. 24		*Eiji Nakayama(1),Motonori Higashinaka(2) 1:unaffiliated,2:JGI Inc.
Nov. 24	16:00 - 17:30　　　 When a shallow methane gas layer is targeted for elastic wave exploration by using the high frequency, the size of the methane bubbles existing in the pores cannot be ignored with respect to the wavelength. It becomes necessary to deal with the effects of resonance vibration of bubbles. In a sand layer containing gas, the purpose is to verify of the phenomenon shown by Anderson and Hampton (1980)'s theoretical formula regarding the elastic wave velocity and the frequency dependence of elastic wave attenuation caused by the resonance vibration of bubbles accompanying wave propagation. We attempted to experimentally observe the resonance phenomenon of transmitted waves. As a result, a significant resonance phenomenon was confirmed. It is often understood that the P-wave wave propagation energy is attenuated when bubbles are mixed in the sand layer, but here it was observed that a large amount of energy was propagated due to the resonance phenomenon. In addition, as a result of investigating the propagation characteristics of S-waves in sand layers containing gas, it was observed that S-waves are more sensitive to changes in bubbles staying in the sand layer than P-waves.	P-15) Laboratory measurement of ultrasonic wave propagation in gas-bearing sand sediments
Nov. 24		*Jun Matsushima・Makoto Suzuki・Pingchuan Zhong・Katsunori Mizuno(1) 1:Univ. of Tokyo


Nov. 25 Room No.1 (Conference Room 61, 6F)

Session	Proposed Sessions: Non-destructive exploration for infrastructure maintenance
Chair	Yo Kitamura (JX Nippon Exploration and Development Co.,Ltd.)

Nov. 25	10:00 - 10:20　　　 Many Japanese domestic water supply and industrial water systems have reached more than 40 years of legal service and are now ageing. The corrosion of water pipelines is known to have a high relationship with the resistivity of the soil. Some municipalities have been conducting excavation surveys. However, this method is costly, time and labour intensive, and difficult to operate on a large scale. Therefore, AIST has been developing a survey technique to determine corrosive soils by measuring soil resistivity on asphalt and concrete surfaces using VLF-band alternating current (VLF-AC) and measuring the resistivity of soil at the depth where the water pipes are buried. This technique is anticipated to contribute to the determination of replacement precedence for ageing water pipes.	11) Investigating corrosive soil conditions around buried water pipelines using VLF band alternating current (VLF-AC) electrical resistivity survey
Nov. 25		*Motoharu Jinguuji・Toshiyuki Yokota(1) 1:AIST
Nov. 25	10:20 - 10:40　　　 The leakage accidents at water facilities are increasing in Japan. One of the causes of these accidents is considered to be the corrosion of water pipes. It is known that the corrosion of water pipes depends on the resistivity of the surrounding soil. Conventional methods for measuring the resistivity of soil have required measurement using soil samples taken by excavation or stripping the pavement. The VLF- AC resistivity survey system developed by the National Institute of Advanced Industrial Science and Technology (AIST) can efficiently investigate the resistivity distribution of the ground from the top of the pavement. Therefore, this system may be useful in assessing the risk of corroded soil. Our company received the technology transfer of the VLF-AC resistivity survey system from AIST and created the same system in-house. We have had the opportunity to conduct a demonstration experiment of this system in the existing water pipe area of Hitachi City, and we will report the result of the experiments.	12) Demonstration Experiment using the VLF-AC Resistivity Survey System in Hitachi City
Nov. 25		*Masayoshi Chidori・Hideki Kouno・Tomoyuki Kaneda・Fumio Suzuki・Hideaki Ugawa・Ryouhei Koga・Shigeki Kawamura(1),Katsuaki Karino(2),Motoharu Jinguuji(3) 1:NGP,2:Geolight,3:AIST
Nov. 25	10:40 - 11:00　　　 VLF-AC electrical resistivity survey system can be applied for simple multi-point vertical soundings. On the other hand, many infrastructures such as water pipelines extend over long distances, so a towed system is considered more suitable. Furthermore, the PVA sponge electrode used by the VLF-AC survey system is non-insulating. Therefore it was necessary to check whether the resistivity measurement would be affected by the change in ground resistance during the moving process. Consequently, we conducted a comparison between the method of pausing and continuous towing. As a result, the paused measurement method obtained results with good reproducibility, whereas the moving process had problems with GPS accuracy.	13) Development of a towed VLF-AC electrical survey system using UGV
Nov. 25		*Motoharu Jinguuji・Toshiyuki Yokota・Ryosuke Umezawa(1),Kento Ide(2),Yoshiaki Karino(3),Masayoshi Chidori・Bunta Suzuki・Hideki kohno(4) 1:AIST,2:Waseda University,3:Geolight,4:NGP
Nov. 25	11:00 - 11:20　　　 VLF (band) alternating current (VLF-AC) electrical resistivity survey uses VLF band (20k Hz) AC. In this condition, the apparent resistivity of VLF-AC shows lower values than that of direct current electrical resistivity survey by skin effect when the length of the dipole is increased, or the resistivity of the underground is high. To deal with the skin effect, we focused on the electromagnetic (EM) analysis methods. The usual electrical analysis methods couldn’t adjust the frequency, but EM methods could. Therefore, we calculated VLF-AC resistivity by EM methods, and investigated the impact of the skin effect and considered the exploration of the deep depth by VLF-AC.	14) A study of skin effect for application to deep depth using VLF (band) alternating current (VLF-AC) electrical resistivity survey
Nov. 25		*Kento Ide・Takumi Ueda(1),Toshiyuki Yokota・Motoharu Jinguuji(2) 1:Waseda Univ.,2:AIST
Nov. 25	11:20 - 11:40　　　 Electrical survey methods without casting electrode into the ground surface have been developed as simple and efficient survey methods. One of them is a VLF alternative current electrical survey method using polyvinyl alcohol (PVA) sponge as a non-destructive electrode. However, it is pointed out that this method has a problem in performing the deep survey comparing the direct current (DC) electrical survey, because the accuracy of apparent resistivity decreases at deeper depths due to the skin effect caused by the frequency of 20 kHz. Since PVA sponge electrodes are non-insulating electrodes different from capacitor electrodes used in many non-destructive electrodes, it is considered that they can be used even in resistivity measurement using DC. If that is possible, the applicability of electrical exploration with PVA sponge electrodes will be greatly increased. Therefore, in this study, the applicability of DC electrical survey using PVA sponge electrodes were investigated. Electrical surveys using standard electrode and those using PVA sponge electrodes were conducted on the same survey line. In addition, 2D electrical survey were also carried out using both types of electrodes, and the results were compared. The results showed that the non-destructive electrodes gave almost the same results as the casting electrodes.	15) DC electric survey using non-destructive electrode
Nov. 25		*Ryosuke Umezawa・Motoharu Jinguuji・Toshiyuki Yokota(1) 1:AIST
Nov. 25	11:40 - 12:00　　　 In recent years, several types of drones such as unmanned aerial vehicles (UAV) and unmanned ground vehicles (UGV) have been developed and applied in various fields. UAV and UGV could be useful tools for the geophysical investigation of shallow subsurface problems at depths of meters to dozens of meters below the surface, which are of concern in fields such as infrastructure maintenance, environmental geology, and civil engineering. In particular, the demand for shallow subsurface exploration over a wide area and along a lengthy survey line without the need to dig up the ground is rapidly increasing. In response to these needs, we have begun to develop a new UGV electromagnetic (EM) exploration system (UGVEM system), which consists of a single-frequency multi-coil electromagnetic probe and UGV. In this research, field experiments were conducted along part of the River-bank in Koga City, Ibaraki Prefecture, Japan. According to the data acquired from field experiments with our new system and apparent resistivity cross-sections generated by the observed data, we were able to conclude that the developed system can be applied for efficient field explorations of shallow subsurface geo-electrical structures.	16) Fundamental study of a multi-coil electromagnetic exploration system using an unmanned ground vehicle
Nov. 25		Kai Satake・Kento Ide・Karin Manzawa・*Takumi Ueda(1),Motoharu Jinguuji・Toshiyuki Yokota・Shogo Komori(2) 1:Waseda Univ.,2:AIST


Nov. 25 Room No.3 (Small Hall 2, 5F)

	Special Sessions: Application of microtremor survey in the creation of 3D subsurface model
Chair	Yuji Mitsuhata (AIST)

Nov. 25	13:20 - 13:40　　　 The National Institute for Land and Infrastructure Management has announced new guidelines for assessing the risk of liquefaction in the ground. This guideline is characterized by creating a three-dimensional subsurface model and calculating the maximum acceleration by seismic response analysis. This guideline describes in detail the method of creating a three-dimensional subsurface model, and exemplifies the application of microtremor survey. In this paper, the items to apply the geophysical survey which described in the guideline are shown, and the contents are described to be the introduction part of a series of presentations on the case study of the microtremor survey.	101) Application of microtremor survey in the creation of 3D subsurface model for a liquefaction evaluation of infrastructure facilities.　(Introduction)
Nov. 25		*Takao AIZAWA(1),Akiyoshi TSUCHIYA(2) 1:Suncoh Consultants,2:JGCA
Nov. 25	13:40 - 14:00　　　 3D microtremor survey has been carried out to create 3D subsurface model for a liquefaction evaluation at an area of 520 m by 640 m in Fukashiba district, Kamisu, Ibaraki, where houses and roads were severely damaged by the liquefaction occurred at Tohoku Earthquake in 2011. Because of the limited access for the survey, irregular arrays with small receiver spacing and grid arrays with large receiver spacing were combined to obtain reliable subsurface S-wave velocity structure from shallow to deep depth interval. The receiver spacing of the small arrays was 5m, while that of the large arrays was about 40 m. Dispersion curves were calculated from total 57 array measurements by CMP-SPAC method, and 3D S-wave velocity model were obtained by the non-linear least square method. A depth slice of the surface to 5m depth from the 3D S-wave velocity model and iso S-wave velocity map show good agreement with liquefaction damages of houses and roads, sand boiling points, and past mined areas investigated by existing literatures. Therefore, we concluded that the 3D microtremor survey helps us to create reliable 3D subsurface model to be used in the liquefaction analysis.	102) Application of microtremor survey in the creation of 3D subsurface model for a liquefaction evaluation of infrastructure facilities. (Part 1) - Comparison between liquefaction damages in the past mined areas and 3D microtremor survey result in Kamisu city-
Nov. 25		*Chisato Konishi・Haruhiko Suzuki・Shunsuke Hamada・Koichi Hayashi(1),Akiyoshi Tsuchiya(2) 1:OYO Corporation,2:JGCA
Nov. 25	14:00 - 14:20　　　 Microtremor survey was carried out to obtain the S-wave velocity structure and create three-dimensional subsurface model for the evaluation of liquefaction. The survey area is the Tokushima, Fukuoka, and Miyazaki area where there is a possibility of liquefaction. The survey design were selected 1D,2D, and 3D array depending on the situation because the three area are urban area. The survey depth is about 100m in 1D survey and 50m in 2D and 3D survey. The engineering bedrock (Vs≧300m/s) and low velocity area were obtained from the S-wave velocity structure. And, these results are almost consistent with existing boring results, and PS logging results.	103) Application of microtremor survey in the creation of 3D subsurface model for a liquefaction evaluation of infrastructure facilities. (Part 2) - Results of 1D-3D microtremor survey in Tokushima, Fukuoka, Miyazaki area -
Nov. 25		*Kazunori Murata・Shunichiro Ito・Tomoko Emoto・Takao Aizawa(1),Akiyoshi Tsuchiya(2) 1:Suncoh Consultants,2:JGCA
Nov. 25	14:20 - 14:40　　　 This study reports the results of 3D microtremor survey which were conducted for creating 3D subsurface model for the evaluation of liquefaction of infrastructure facilities in Niigata City, etc. As a result of the survey in Niigata city, the 3D S-wave velocity structure which was up to a depth of approximately 50 m was estimated. The estimated S wave velocity structure was mostly consistent with the terrain classification. A depressed structure of S wave velocity was estimated as well as the 2D surface wave survey. In addition, 3D microtremor survey was seemed to utilize the estimate of the depth of deep engineering bed rock because the estimated S wave velocity profile showed the average trend of that of PS logging and the estimated depth of engineering bed rock was mostly consistent with that of PS logging result in the surrounding area.	104) Application of microtremor survey in the creation of 3D subsurface model for a liquefaction evaluation of infrastructure facilities.(Part3) - Investigation of its applicability of 3D microtremor survey in Niigata city -
Nov. 25		*Daisuke Ohara・Masahiro Kurokawa・Norikazu Abe・Jun Teruya(1),Akiyoshi Tsuchiya(2) 1:Nippon Koei,2:JGCA


	Executive Sessions
Chair	Keiichi Suzuki (Kawasaki Geological Engineering Co., Ltd.)

Nov. 25	15:00 - 16:00	Professor Shuichi Hasegawa (Kagawa University)
Nov. 25	15:00 - 16:00
Nov. 25	16:00 - 17:00	Masaaki Kagawa (third-generation president of Sanuki Mengyo Co.)
Nov. 25	16:00 - 17:00


Nov. 26 Room No.1 (Conference Room 61, 6F)

Session	[Disaster Prevention 1][Earthquake 1]
Chair	Kazunori Murata (Suncoh Consultants Co., Ltd.)

Nov. 26	9:30 - 9:50　　　 An integrated ground model for seismic ground motion prediction, covering the regional and shallow-to-deep structures, is being constructed in the vicinity and surrounding areas of Enasan-Sanageyama_kita Fault Zone. As part of this work, we analyzed the basement structure using gravity data. The analysis is performed in a succession of 1_Bouguer anomaly calculation, 2_filtering, and 3_gravity basement analysis. As the main results of the gravity basement analysis, locally deep structure of basements and overstepping sedimentary basins are revealed within the modeling area. This kind of information cannot be detected through the geological map of this area. Thus, one can see the thickness of the sediments in these basins from the depths of gravity basement structures. Moreover, these results effectively make it possible for us to construct the ground structure model for estimating the strong ground motions at earthquakes and to evaluate the fault activities.	17) Gravity data analysis around Enasan-Sanageyama_kita Fault Zone
Nov. 26		*Kota Koshika・Kyozo Nozaki・Masao Komazawa・Hisanori Matsuyama・Atsushi Yatagai(1),Shigeki Senna・Hiroyuki Fujiwara(2) 1:OYO Corporation,2:National Research Institute for Earth Science and Disaster Prevention
Nov. 26	9:50 - 10:10　　　 A blind prediction of strong ground motions observed at a test site during the main shock and one of foreshocks of the 2016 Kumamoto earthquake was conducted in the 6th International Symposium on the Effects of Surface Geology on Seismic Motion in August, 2021. The unpublished strong motion records at the test site in the Kumamoto plain were estimated using provided strong and weak motion records at a rock site located in a mountainous area near the test site. In this study we have conducted microtremor and surface-wave explorations around the rock site to know a 1D S-wave profile. Rayleigh wave phase velocities in a frequency range of 4 to 100 Hz were obtained in the explorations. We estimated an S-wave profile of the shallow and deep sediments over a basement with an S-wave velocity of about 3.2 km/s from the phase velocity inversion. The deep sediments are responsible for a peak of the amplification at a frequency of about 3 Hz, while peaks at a frequency range of 8 to 12 Hz are due to the effects of the shallow thin layer.	18) S-wave exploration at rock site for blind prediction of strong ground motion of the 2016 Kumamoto earthquake
Nov. 26		*Hiroaki Yamanaka(1),Seiji Tsuno(2),Michiko Shigefuji・Tatsuo Kanno(3),Nobuo Takai(4),Takeshi Matsushima(3) 1:Tokyo Inst. Tech.,2:Railway Tech. Res. Inst.,3:Kyushu Univ.,4:Hokkaido Univ.
Nov. 26	10:10 - 10:30　　　 To quantitatively evaluate the effects of seasonal variation in the physical parameters of surface ground due to the freezing in the cold region, we carried out various geophysical observations and surveys such as, continuous seismic observation, surface wave exploration, and so on, in Kitami city. As a result, in both the seasonal variation characteristics of the weight drop excitation and the seismic data, remarkable differences in phase velocity and spectral ratio were observed between the winter and other seasons.	19) Study on the site amplification characteristics in the cold region by the geophysical explorations at Kitami city: Characteristics of seasonal variation of weight-drop excitation data and seismic data
Nov. 26		*Seiji Tsuno(1),Hiroaki Yamanaka(2),Nobuo Takai(3),Shunzo Kawajiri(4),Naofumi Nakagawa(3),Shingo Nomoto・Jun Horita(5),Michiko Shigefuji(6) 1:RTRI,2:Tokyo Tech.,3:Hokkaido Univ.,4:Kitami Tech.,5:Geotech.,6:Kyushu Univ.
Nov. 26	10:30 - 10:50　　　 It is important to understand the site amplification characteristics as earthquake damage. The authors have proposed a method for simply evaluating the ground hazard value using the H/V spectral ratio of microtremors. In this paper, the validity of the method was examined using the damage caused by the 1923 Kanto Earthquake and the 2016 Kumamoto Earthquake. For both earthquakes, a positive correlation was confirmed between the proposed hazard evaluation value PE and building damage. If the PE is the same, the damage caused by the Kumamoto earthquake is smaller. This may be due to the difference in construction age.	20) Comparison of building damage caused by an earthquake and microtremor H/V spectral ratio -For the 1923 Kanto Earthquake and the 2016 Kumamoto Earthquake-
Nov. 26		*Tsutomu Ochiai・Takahisa Enomoto(1) 1:Kanagawa University


Session	[Earthquake 2][Disaster Prevention 2]
Chair	Seiji Tsuno (RTRI)

Nov. 26	11:10 - 11:30　　　 Joint analysis of receiver function and autocorrelation was performed to estimate the P- and S-wave velocities with the depth to the seismic bedrock using strong motion records observed in the Shimousa region. We measured S-wave velocity and sediment thickness from H-k stack of the vertical and transverse components of autocorrelation and Ps and PpPs converted waves in the receiver function. Our previous model using only transverse autocrrelation in Narita City shows good agreement while some other stations in the Shimousa region require improvement of the structure model including P-wave velocity. Since H-k stack requires an assumption of P-wave velocity, further improvement of P-wave velocity structure model is important to compare with the observed receiver function.	21) Velocity structure estimation in the Shimousa region from joint analysis of receiver and autocorrelation functions of strong motion record based on seismic interferometry
Nov. 26		*Kosuke Chimoto(1) 1:Kagawa Univ.
Nov. 26	11:30 - 11:50　　　 To verify the effectiveness of high-resolution ultra-shallow subsurface imaging using a vibrator source and to validate the feasibility of multi-scale survey from shallow to deep structure, we conducted a small-scale seismic experiment using broadband vibrators. The result of experiment demonstrated that the subsurface structure was estimated seamlessly from weathered layer to pre-Tertiary basement with essential vertical resolution. The combination of broadband vibrator and single sensors with dense spatial sampling was confirmed to have the potential imaging capabilities for multi-scale reflection profiling. High-resolution multi-scale reflection profiling will contribute to depict complicated deep geometry and recent activities of active faults.	22) High-resolution reflection seismic survey for both shallow and deep targets using broadband vibrator
Nov. 26		*Hideo Saito・Mamoru Nakata・Fumitoshi Murakami・Susumu Abe(1),Tatsuya Ishiyama(2),Hiroshi Sato(2,3) 1:JGI,2:ERI,3:Shizuoka University
Nov. 26	11:50 - 12:10　　　 Passive seismic imaging applies imaging conditions directly to seismic data without source information. In this study, we investigated seismic imaging using PS-converted waves, which corresponds to receiver function analysis in seismology, using elastic reverse-time migration (RTM). TheP- and S- wavefields are separated from the back-propagated elastic wavefield and then are correlated to form an image of the conversion points. Imaging results of synthetic seismic data calculated using a simple 2D model reveal the nature and applicability of the proposed method. Application to the synthetic data of a crustal and plate model under Kinki area using different station geometry results in unsatisfactory images, which leads to the necessity of careful processing and investigation.	23) Imaging of PS-converted waves by elastic reverse-time migration: a numerical study
Nov. 26		*Toshiki Watanabe(1),Kazuya Shiraishi(2),Ryota Nakamaru(1) 1:Nagoya Univ.,2:JAMSTEC
Nov. 26	12:10 - 12:30　　　 Distributed acoustic sensing (DAS), which is an emerging seismic acquisition tool, enables us to obtain continuous seismic data at densely spaced points. This study, for first time, uses DAS for monitoring subsurface properties such as phase velocity and seismic wave velocity changes at the closed mine. We analyze ambient noise data of 46 days recorded by DAS cable deployed at Sazare-mine in Ehime prefecture. In the analysis of ambient noise using seismic interferometry, surface wave propagating between two channels and dispersion curve can be successfully estimated from one-day stacked cross-correlation functions. Furthermore, seismic velocity changes estimated using the stretching method show seismic velocity changes have a correlation with precipitations at Sazare-mine. These results suggest that the monitoring using DAS and seismic ambient noise analysis can be a new monitoring technology at the closed mine.	24) Seismic velocity change monitoring using distributed acoustic sensing deployed at Sazare Mine
Nov. 26		*Kota Mukumoto・Takeshi Tsuji・Tatsunori Ikeda(1),Jiro Uesugi(2) 1:Kyushu University,2:Sumitomo Metal Mining Co., Ltd.


Nov. 26 Room No.2 (Conference Room 63, 6F)

Session	[Buried Objects][Urban Geology][Civil Engineering 2]
Chair	Tsuneyoshi Sugimoto (Toin University of Yokohama)

Nov. 26	9:30 - 9:50　　　 To image and monitor the geological formations including reservoirs, we have developed a small-size source system with size of ~10cm. We call this source system “Portable Active Seismic Source” (PASS).Because the signal timing is accurately controlled in the PASS, stacking continuous waveform enhances the signal-to-noise ratio, allowing the use of a small seismic source to explore extensive areas.Furthermore, because the PASS is small and low-cost, we can deploy PASS in many places and continuously monitor the geological formation such as CO2 storage reservoirs. The PASS generates a wide frequency signal, and we can change the source frequency by considering the target of the survey. Here we mainly show the application of our PASS to the distributed acoustic sensing (DAS) data. Because the DAS system enables us to acquire source signals in a long and dense receiver array, our system shows promise for high-resolution and low-cost imaging/monitoring of reservoirs. Because the cable was laid out horizontally in a shallow trench, the DAS system mainly recorded horizontal strain. Our field experiment demonstrated that the signal from the small PASS propagated several hundred meters for horizontal distance. We further identified refracted waves from the PASS by using vertical-component seismometer data.	30) Portable Active Seismic Source (PASS) system for imaging and monitoring
Nov. 26		*Takeshi Tsuji・Junji Kinoshita・Tatsunori Ikeda(1),Jiro Uesugi(2) 1:Kyushu University,2:SMM
Nov. 26	9:50 - 10:10　　　 For imaging ultra shallow subsurface structures at depths of around 2m down to 10m, we are focusing on 3D seismic reflection method and carry out some basic experiments to investigate its applicability, by following the pioneering study (Bachrach and Mukerji, 2001). The preliminary processing results contain diffractions due to structures buried at the depth of 0.4 down to 1.5m. Through these basic experiments, we recognize that this method could be applicable, while it is also necessary to investigate more effective and efficient ways of acquisition and processing. We are planning to carry out field experiments at test fields of which subsurface structures are well clarified, in order accelerate to investigate the subjects above.	31) Basic experiments on the applicability of 3D ultra shallow seismic reflection imaging
Nov. 26		*Takashi Imayoshi・Yosuke Kato(1) 1:Hanshin Consultants
Nov. 26	10:10 - 10:30　　　 Muography is a method that estimates the density distribution inside an object based on observations of the number of muons transmitted through the object. The practical application of muon tomography to diverse targets requires a utilization-focused evaluation of the spatial, temporal, and density resolutions to optimize performance. We conducted 2D muon tomography numerical simulation to evaluate the relationships of those three resolutions. During the simulation, two different inversion methods were used to evaluate and compare their influences on the resolutions. Also, in 2D muon tomography, diagonally coming muons are used but their count rate gets lower as zenith angle of flight direction gets higher. Lower count rate means unstable estimations, so we compared results between 1D muography using muons coming from upper directions and 2D muon tomography using muons coming from diagonal directions. We found that 1D muography provides better results on situations than 2D muography.	32) Utilization-focused evaluation of relationships between spatial, temporal and density resolution of multidimensional density estimation using muon tomography
Nov. 26		*Masashi Kodama・Toshiyuki Yokota(1),Jun Matsushima・Hiroyuki Tanaka(2),Tadahiro Kin・Naoya Okamoto(3) 1:AIST,2:The Univ. of Tokyo,3:Kyushu Univ.
Nov. 26	10:30 - 10:50　　　 Ground Penetrating Radar (GPR) is a geophysical survey technique that records the reflected waves of electromagnetic waves and investigates the buried objects and underground structures by the shape of the waveform. Due to the improvement of data acquisition technology by the technical innovation of GPR and the increase of needs for non-destructive inspection of aging public facilities, there is a need to automate and save the interpretation time for the large amounts of data. On the other hand, due to the remarkable progress of computer technology in recent years, deep learning technology has significantly been developed. As a result, the object recognition ability has been dramatically improved, and application research is actively promoted. Currently, studies applying deep learning to GPR data mainly use two-dimensional depth section images. However, it is believed that more reliable extraction of events can be achieved by making comprehensive decisions from 3D data. In this study, we used a neural network based on 3D convolution, which has been developed in the medical field, to detect events in 3D GPR data.	33) An attempt to detect events by deep learning on 3D GPR data, part 2
Nov. 26		*Ryohei Tottori・Hiroyuki Azuma・Yoshiya Oda(1),Toshifumi Matsuoka(2),Nobuhiro Eki・Yuji Kawamoto(3) 1:Tokyo Metropolitan University,2:Fukada Geological Institute,3:DAIWA Exploration & Consulting Co.,Ltd.


Session	[Metal][Resource Exploration 2]
Chair	Kenji Kubota (CRIEPI)

Nov. 26	11:10 - 11:30　　　 The exploration and development of shallow metallic ore deposit is almost completed. The focus of exploration is shifting to deep blind deposits. Therefore, there is an increasing expectation for geophysical exploration that non-destructively investigates the deep geological structure over wide area. However, interpretation of the geological structure analyzed from geophysical data is often inadequate. One of the reasons is the lack of knowledge about the physical properties of the rocks that form the underground structure. The lack of basic knowledge to associate the distribution of physical properties with the distribution of rocks makes it difficult to interpret the results of geophysical exploration. To overcome this, we designed a database that collects the physical properties of ores and rocks in deposit areas last year. We have completed the prototype of the database and are currently working on its modification for practical use.	34) Development of a rock physical property database to support metal deposit exploration
Nov. 26		*Shinichi Takakura(1) 1:AIST
Nov. 26	11:30 - 11:50　　　 In order to verify the effectiveness of the AMT method for hydrothermal deposit exploration, AMT measurements were carried out in an approximately 2km square area around the Akeshi mine, which is a hydrothermal deposit located in the Nansatsu area, Kagoshima prefecture. The resistivity structure up to a depth of about 1 km was obtained by three-dimensional analysis using the AMT data of 61 sites. The resistivity structure is consistent with the geological structure estimated from surface geological surveys and borehole investigations. Silicified rocks and deep basement rocks show high resistivity, while altered clay zones show low resistivity. The result indicates the AMT method is effective for exploration of hydrothermal deposits at depth.	35) Verification experiment of AMT method for hydrothermal deposit exploration around the Akeshi mine, Kagoshima prefecture
Nov. 26		*Shinichi Takakura・Ryosuke Umezawa・Shogo Komori(1) 1:AIST
Nov. 26	11:50 - 12:10　　　 At the mine, the orebody is usually modeled from information of geological survey and drillings, for the management of ore grade and volume. However, it is difficult to model the orebody when there are few drillings or drillings are not enough length. In this study, high-density electrical prospecting was introduced to solve the above problem. At first, the applicability of this exploration method was examined at Iwado mine producing Au-bearing silicified ore, where the orebody is well modeled by enough drillings. The high-density electrical prospecting was carried out with the electrodes placed at intervals of 5 m. As a result, the resistivity distribution was obtained almost in agreement with the ore model expected from the drillings. Next, high-density electrical prospecting was carried out at Mt. Iwado prospect, where there are few drillings. As a result, the resistivity distribution was in good agreement with the distribution of silicified rocks on the surface and the existing drillings. Furthermore, a high resistivity region, which is considered to be an orebody, was obtained in the area where the orebody has not been known.	36) Application of high-density electrical prospecting for Au-bearing silicified orebody in the Iwado mine, Kagoshima prefecture
Nov. 26		*Yo Kitamura・Ryuya Sato(1),Yuko Miuchi(2),Naoki Ito(1),Ryosuke Umezawa・Shogo Komori・Shinichi Takakura(3),Keiko Koshida(2),Ryohei Nakai(4) 1:JX NED,2:JX NMM,3:AIST,4:Kasuga Mines
Nov. 26	12:10 - 12:30　　　 In the present study, Time-domain Induced Polarization (TDIP) measurements were conducted at Kannnondou Kuroko deposit, Akita, Japan. IP Fullwave data were successfully recorded from 1 milliseconds to 2 seconds after current-off, using Iris Syscal Pro and Hioki data logger MR8875. The Observation showed that yellow ore-bearing sediment has extremely low apparent resistivity and maintains high apparent chargeability throughout the current-off period, comparing black ore-bearing sediment. Cole-Cole parameters distribution estimated from fullwave inversion by Aarhus Workbench with ERT/IP module suggests a clear contrast of time constant (τ) and intrinsic chargeability (m) between the yellow ore and black ore zones, noting that the inversion analysis is still ongoing.	37) An attempt to estimate Cole-Cole parameters distribution from TDIP fullwave data – a case study at Kannondou Kuroko deposit, Akita, Japan
Nov. 26		*Shogo Komori・Shinichi Takakura(1),Satoshi Ueda・Kazuo Masuda・Takafumi Murakita(2) 1:AIST,2:JOGMEC

VENUE
	Sunport Hall Takamatsu, 2-1 Sunport, Takamasu City, Kagawa, Japan and ONLINE

SCHEDULE
	Wednesday, November 24, 2021
		Openning Speech	Room No.1 (Conference Room 61, 6F)	09:50-09:55
		__Speaker:	Toshiki WATANABE (NAGOYA Univ.; President of SEGJ)
		Technical Sessions	Room No.1 (Conference Room #61, 6F)	10:00-14:40
		Technical Sessions	Room No.2 (Conference Room #63, 6F)	13:00-14:40
		Poster Core Time	Room No.1 (Conference Room #61, 6F)	15:00-17:30
		Student Exchange Event	Special Venue	17:40-18:50

	Thursday, November 25, 2021
		Technical Sessions	Room No.1 (Conference Room #61, 6F)	10:00-12:00
		Special Sessions	Room No.3 (Small Hole #2, 5F)	13:00-14:40
			Application of Microtremor Exploration for Creating a 3D Ground Model
		Executive Sessions	Room No.3 (Small Hole #2, 5F)	13:00-15:00
		__Chair:	Keiichi SUZYKI (Kawasaki Geological Engineering Co. Ltd; Vice-President of SEGJ)
		__Presentation(1):	Geophysical Exploration Utilization Technique for Applied Geological Researcher Shuichi HASEGAWA (Kagawa Univ.)
		__Presentation(2):	Whether I'm in Dreaming or Awaking, UDON (Japanese Noodles) is always on my mind. Masaaki KAGAWA (President of Sanuki Mengyo Co. Ltd.)
	Friday, November 26, 2021
		Technical Sessions	Room No.1 (Conference Room #61, 6F)	09:30-12:30
		Technical Sessions	Room No.2 (Conference Room #63, 6F)	09:30-12:30
		Field Trip	Room No.1	13:20-16:30

Registered and Paid		Pre-Registration (Until November 4,2021)	Onsite Registration
Conference Meeting	Member / Non-member	JPY 7,700-*	JPY 8,800-**
Conference Meeting	Student	JPY 3,850-*	JPY 4,400-**
Field Trip	Member / Non-member	JPY 3,300-*	JPY 3,300-*
Field Trip	Student	JPY 0,000-**	JPY0,000-**

**	Pre-registrant will receive PAPER Proceedings at the registration desk of the conference.
**	PAPER Proceedings can be purchased at a price of JPY 1,650-.

DESTINATION
	Iwase-Oyama Tumulus
		Stone Mound Tumulus located at Mt. Iwase-Oyama


SCHEDULE
	Friday, November 26, 2021
		Departure from VENUE after the monring technical sessions around 13:30. Visit to Iwase-Oyama Tumulus. Arrival at Takamatsu Station around 16:30.


	More information about the field trip will be sent to those who have pre-registered the field trip.

CANCELLATION
	No Refund Will Be Made.

LIST OF ADVERTISEMENTS
	Geophysical Surveying Co., Ltd.(GSC) ITOCHU Techno-Solutions Corpration(CTC) JGI, Inc. Kawasaki Geological Engineering Co. Ltd.(KGE)

1) TEST for you internet connection to the online conference
2) Guide for Technical Session
3) DO NOT screenshot or record any part of the conference (including the audios).