Earthquake Monitoring Using Dense Local Seismic Network, As-Net, in Northern Tohoku, Japan

Abstract eng:
We report site characteristics and detailed earthquake activity derived by AS-net, the local high-sensitivity seismic observation network we have installed covering northern Tohoku and southwestern Hokkaido, Japan. The AS-net consists of 36 stations covers the region where the stations have been sparse compared to the other. The AS-net have been installed from 2013 to 2014 and started real-time observation at August 2014. After the installation, we investigated the site characteristics and data quality of each station. We derived averaged P- and S-wave velocity from surface to the seismometer installed at the bottom of ~20 m deep borehole by means of downhole method. We found that the averaged velocities are small at the region covered by thick deposit. We also found that the noise level at each station derived from the root-mean-square for amplitude of ambient noise is higher at the region covered by thick deposit. The noise level at the station which have the averaged S-wave velocity less than 350 m/s is obviously higher than the other. Then we determine the hypocenters for the earthquakes occurring around the AS-net using data derived by AS-net and other stations. The 5003 hypocenters for earthquakes occurred from January 2014 to December 2015 have been determined. In terms of shallow crustal earthquakes, we derived 2.6 times as many earthquakes as that listed in JMA catalogue at the same region and period. This earthquake catalogue shows that we can investigate the earthquake activity in rich detail utilizing AS-net.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket