11:20 AM - 11:35 AM
[SSS28-03] Passive monitoring of groundwater using elastic waves
In order to estimate the detailed structures in the shallow (~ a few tens of metes) part and their temporal changes, we placed a seismometer at the toe side of a landslide area. We selected the landslide located in Shiga Prefecture, which is shown in the landslide distribution map by NIED. Springs are observed inside the landslide area, suggesting the ground water level is very shallow.
Seismic waveforms are recorded at the sampling frequency of 200 Hz. Travel times of the phases related to the shallow structure are considered to be short, which implies that we need larger sampling frequency. Therefore, we interpolated the raw data using cubic spline functions to obtain the waveform data every 1 ms. Then, we calculated the auto-correlation functions using 1 day records, followed by whitening process. As a result, we detected coherent phases with the travel time less than 1 s. In the next step, we discuss the cause and the temporal changes of these phases together with the changes of noise sources.