Abstract
This article describes improvement of the rapid earthquake analysis system, accurate and quick analysis system for source parameters (AQUA), which has automatically determined the location, magnitude, and fault type of M 7 except nearly simultaneous events. Source parameters with and without fixed horizontal locations are provided within 100–250 and 100–600 s of the first P arrival, respectively. This system is valuable for disaster mitigation because it rapidly provides information for use in tsunami warning and early damage assessment.
Highlights
W E HAVE maintained a rapid seismic source-parameter determination system called the accurate and quick analysis system for source parameters (AQUA), since 2005 [1], with the aim of rapidly determining earthquake source parameters such as location, event size, and faulting style
We report results of significant recent earthquakes (Mw 7.0–7.9) and discuss the quality of the AQUA catalogue based on the determination ratio, accuracy, and processing time
We evaluate determination ratio of AQUA, which we define as ratio of number of identical events in AQUA divided by event number in Japan Meteorological Agency (JMA) catalogue under certain conditions supposing that JMA catalogue lists all events
Summary
W E HAVE maintained a rapid seismic source-parameter determination system called the accurate and quick analysis system for source parameters (AQUA), since 2005 [1], with the aim of rapidly determining earthquake source parameters such as location, event size, and faulting style. The CMT solution has several advantages over slower, more conventional methods as follows: 1) long-period waveforms suffer little effects from structural heterogeneity along the propagation path; 2) the CMT solution is determined by analyzing the entire waveform and does not require accurate arrival time picks, polarities of first motions, all of which can be difficult, even for skilled analysts; and 3) the event size estimated from the CMT solution (the seismic moment Mo or moment magnitude Mw) has a clear physical definition and relates to the size of the fault motion, even for giant earthquakes, whereas a traditional magnitude (M) determined from shortperiod waveform amplitudes with an empirically calibrated scale tends to underestimate the size of a large earthquake [11], [12], when only the initial part of the waveform is used [13] These advantages improve the stability of automatically generated solutions. AQUA analysis was further affected because the source duration was so long that the gap between the earthquake origin time (i.e., the initiation of fault rupture) and centroid time was larger than the algorithm typically allowed, so a final solution could not be obtained
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