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May 12, 2008 Sicuang earthquake
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1. Station distribution

Seismic stations operated by Chinese earthquake center are shown in Fig.1. The closest station is CD2 and 32km from the epicenter. Most of the records are clipped at S-wave but P-wave is recorded clearly.
Fig.1. Station Distribution.

2. Analysis

Magnitude is estimated from P-wave record using Tau_c method (Wu and Kanamori, 2005). Most of the stations except CD2 are at the distance more than 500km, so only CD2 data are processed. The result shows the computed tauc was 2.55. In Fig.2, tauc value of other large earthquakes are shown. From this result, the initial period of the rupture is smaller as this size of the event.


Fig.2. Tauc values of many events.


Fig.3. Displacement waveform and original waveform of the closest station CD2 [cm, cm/s].

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   CD2 103.758 30.910 2.552 179.520 38.581
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Table1. Analytical results using Tau_c method (Wu and Kanamori, 2005). Station ID, Station longitude, latitude, tauc, P-arrival time, epicentral distance(km) from the left.

Reference
Wu, Y. M. and H. Kanamori (2005). Experiment on an onsite early warning method for the Taiwan early warning system, Bull. Seism. Soc. Am., 95, 347-353.