Q_p 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 deduce the three-dimensional Q_p structure beneath Taiwan. The data consist of three-dimensional, digital seismograms of 98 earthquakes with magnitudes between 2.2 and 5.7. The Q_p structure was obtained by the damped least-square method from attenuation time values (t*) and travel times. Attenuation time values (t*) were calculated from 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 Q_p values in the Taiwan area correlate well with the seismicity. In the upper crust (depths of between 0 to 10 km), the lower Q_p 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 Q_p values.