We have developed a real-time moment tensor monitoring system (RMT) which takes advantageof a grid-based moment tensor inversion technique and real-time broad-band seismicrecordings to automatically monitor earthquake activities in the vicinity of Taiwan. The centroidmoment tensor (CMT) inversion technique and a grid search scheme are applied to obtainthe information of earthquake source parameters, including the event origin time, hypocentrallocation, moment magnitude and focal mechanism. All of these source parameters can bedetermined simultaneously within 117 s after the occurrence of an earthquake. The monitoringarea involves the entire Taiwan Island and the offshore region, which covers the areaof 119.3°E to 123.0°E and 21.0°N to 26.0°N, with a depth from 6 to 136 km. A 3-D gridsystem is implemented in the monitoring area with a uniform horizontal interval of 0.1° anda vertical interval of 10 km. The inversion procedure is based on a 1-D Green's functiondatabase calculated by the frequency-wavenumber (fk) method. We compare our results withthe Central Weather Bureau (CWB) catalogue data for earthquakes occurred between 2010and 2012. The average differences between event origin time and hypocentral location areless than 2 s and 10 km, respectively. The focal mechanisms determined by RMT are alsocomparable with the Broadband Array in Taiwan for Seismology (BATS) CMT solutions.These results indicate that the RMT system is realizable and efficient to monitor local seismicactivities. In addition, the time needed to obtain all the point source parameters is reducedsubstantially compared to routine earthquake reports. By connecting RMT with a real-timeonline earthquake simulation (ROS) system, all the source parameters will be forwarded tothe ROS to make the real-time earthquake simulation feasible. The RMT has operated offline(2010-2011) and online (since January 2012 to present) at the Institute of Earth Sciences(IES), Academia Sinica (http://rmt.earth.sinica.edu.tw). The long-term goal of this systemis to provide real-time source information for rapid seismic hazard assessment during largeearthquakes.
- Computational seismology
- Earthquake source observations
- Inverse theory
- Seismic monitoring and test-ban treaty verification
- Time-series analysis