| Summary: | 碩士 === 中國文化大學 === 地學研究所地質組 === 106 === In this study, we used teleseismic P-waves and damped least-squares time-domain deconvolution with smoothing and non-negative constraints to analyze systemically source time functions (STFs) for 14 moderate- and large-sized earthquakes (Mw 5.5-7.5) from 1996 to 2018. Afterwards, using elimination method to decompose the STF can further infer multiple-event features for each earthquake studied. From sub-events decomposed from the STF, source parameters, including seismic moment (M0), radiated seismic energy (ES), source duration (T), and static stress drop (S), were obtained. First, for rapidly estimate the STF, only stations perpendicular to the rupture direction were selected to complete the non-negative time-domain convolution with empirical Green’s functions (EGFs), which were synthetic teleseismic P-waves without source duration created at the position of main shock. Secondly, for accelerating the non-negative time-domain deconvolution, we used 400 data points and damping value of 100 to the deconvolution by testing. This made the STF not too smooth and retained some details in the STF. Thirdly, a depth testing was done to gain the optimal focal depth for each earthquake. This would decrease the trade-off between focal depth and source duration. Finally, we used a statistical method, AICc, to reasonable judge the time-length of source duration. Results showed high-frequency ES to be caught from the multiple-event analysis. In addition, the average S can be also calculated using multiple sources instead of a single source. The ratio ES/M0 was proportional to S not only among earthquakes but also during each earthquake rupture. For earthquakes in Taiwan, the ratio ES/M0 was 1-510-5 and S was 3-130 bars with the average of 35-50 bars, which were consistent with global observations. The relationship between M0 and T also correspond with a power law, M0~T3. The ratio M0/T3 was close to a value for global observations, but lower than that for earthquakes in Mexico. As a whole, the results from this study were consistent with previous studies or global observations. This also showed that the non-negative time-domain deconvolution developed from this study could stably estimate the STFs for moderate- and large-sized earthquakes in Taiwan. In future, we will use the method to regional data to estimate the STFs for small-sized earthquakes.
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