SEGJ Technical Conference

Seismic time lapse experiments in the old quarry and the relation to the past subsidence area

Abstract We carried out the seismic time-lapse experiment in an old quarry region. We used an electro-magnetic seismic source to maintain the same vibration condition at the same position in each one week in July and August, 2014, respectively. We used a number of buried geophones and two borehole seismometers at 70m and 200m depth. The area is approximately 3 km x 4 km. The sweep frequency was from 10 to 50Hz during 100 seconds. We obtained the transfer function by division of one hour stacked data by the source signature. The calculated transfer functions during two months show very subtle changes except later arrivals. The later arrivals could be surface waves travelling near surface sediment layer. The effect of rainfall in July are not so large in contrast to the case of Awaji Island in February 2011. We compute the residual P-waveforms and back-propagated those from the receivers. The obtained images suggest some good correlation with the imaged direction and past subsidence region.