Development of Accurate and Quick Analysis System for Source Parameters (AQUA)

We have developed an automatic system called the Accurate and QUick Analysis System for source parameters (AQUA System) that provides rapid estimates of hypocenter location, magnitude, and moment tensor for medium to large-scale earthquakes that occur near or underneath Japan. The AQUA System monitors high-sensitive real-time seismic waveform output from the Hi-net operated by the National Research Institute for Earth Science and Disaster Prevention (NIED). Upon detecting an earthquake, the AQUA System provides an estimate of the event’s hypocenter and magnitude within 15-30 seconds. Within a further 2-10 minutes, the system provides centroid moment tensor (CMT) solution by inversion technique using broadband seismic waveform of NIED F-net. To assess the accuracy of the new system, we compared hypocenter and magnitude data derived from the AQUA System over the period from September 2004 to August 2005 with catalog data from the Japan Meteorological Agency (JMA). We also compared CMT solutions derived from the AQUA System with corresponding values from the NIED F-net and catalog data of Harvard University’s CMT Project. A total of 339 seismic events were detected during the period of analysis. The AQUA System determined hypocenters for 324 of these events and CMT solutions for 224 events. The estimated hypocenters are within 10km horizontally and 20km vertically of the hypocenters calculated by the JMA in 80% of cases, and the CMT solutions were approximately the same as those obtained from other systems. The results of analyses by the AQUA System are published on the website of NIED Hi-net.