| Summary: | 碩士 === 國立中正大學 === 地震研究所 === 99 === Earthquake early warning has become an important task in seismic hazard prevention. The purpose of this research is to use intrinsic attenuation of dispersive P-wave, Qp, to serve as an earthquake precursor. On November 5, 2009, an earthquake (ML=6.3; depth=24km) occurred in Mingjian, Nantau area, Taiwan. Vertical-component of first-cycle P-wave data recorded by the CWBSN (the Central Weather Bureau Seismic Network) from 2009/01 to 2009/07 is used to obtain Qp parameter. For better resolution, we have applied the Newton polynomial interpolation method to down sampling the data to interval of 0.001 sec. Then the Multiple Filter Technique is used to obtain frequency-time curve, which leads to an optimized Qp determined by the Genetic algorithm method. Our results indicate that 2-month before the occurrence of an earthquake with ML=5.4, the Qp is beginning to decrease for all stations, which implies that the crustal area becomes more fractured due to highly stress accumulation. We conclude that Qp is very sensitive to the change of stress state and can serve as a key index in earthquake early warning.
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