Qp Structure in the Taiwan Area and Its Correlation to Seismicity


The seismic waveform data recorded by the Taiwan Telemetered Seismographic Network (TTSN) were used to duduce the three-dimensional Qp structure beneath Taiwan. The data consist of three-dimensional,digital seismograms of 98 earthquakes with magnitudes between 2.2 and 5.7. The Qp structure was obtained by the damped least-square method from attenuation time values (t*) and travel times. Attenuation time values (t*) and travel times. Attenuation time values (t*) were calculated form these events by using a spectral decay technique under the assumption of that t* is independent of frequency. P-wave spectra were corrected for a source spectrum of ω2 model. Least-square fitting was done in the frequency domain of 4 to 25 Hz. Frequencies above 25 Hz are usually avoided due to the uncertainty of instrument correction. Our results show that the distribution pattern of Qp values in the Taiwna area correlate well with the seismicity. In the upper crust (depths of between 0 to 10 km), the lower Qp area is consistent with an area of higher seismicity. However, in the lower crust (10 to 25 km) and upper mantle, the area of higher seismicity is consistent with higher Qp values.

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