Observations of Anomalous Seismic Attenuation and Evidence of a highly attenuative aseismic zone in the active collision orogen of Southeastern Taiwan.
Reporter : Chen Jo-Hao
Abstract
Using data from a linear seismic array, we investigate the seismic attenuation across an aseismic zone in the southeastern Central Range Taiwan. According to ω 2 model, we fit the amplitude spectra of P and S waves with a theoretical spectrum to obtain the attenuation parameter t. Next, we plot three figures of parameter t versus travel time, back azimuth and focal depth, separately. From the figures, we find out that there is an unusual distribution of parameter T in eastern station of Taiwan. Besides, we also see that, by using 2D raytracing method and inverted Qp and Qs of two profiles, they both exist anomalous zone in depth 15~20km and 15~25km, respectively. From Q model, we can found that the high-temperature and possible presence of fl uids are in high-attenuation zone. It just matches with the aseismic zone and low-velocity zone. B y combinations of several geophysical evidences , the aseismic zone is probably caused by active geothermal or partial melting processes in the intense collision orogeny.
Reference
Lee, C.P., Hirata, N., Huang, B.S., Huang, W.G., Tsai, Y.B., 2009. Anomalous seismic attenuation along the plate collision boundary in southeastern Taiwan: observations from a linear seismic array. Bulletin of the Seismological Society of America, Vol. 99, No. 5, pp.2662–2680, October 2009.
Lee, C.P., Hirata, N., Huang, B.S., Huang, W.G., Tsai, Y.B., 2009. Evidence of a highly attenuative aseismic zone in the active collision orogen of Taiwan. Tectonophysics 489, pp.128–138, April 2010.