汶川大地震前非台风扰动现象的研究

为了区分汶川大地震的震前扰动现象中的台风因素和非台风因素,本文研究了中国大陆宽带地震仪在汶川大地震前记录到的异常扰动信号的时频特征.研究结果表明汶川大地震的震前扰动主要由两种扰动构成,二者动态特征完全不同.其中优势频率为0.2～0.25 Hz的扰动主要与台风Rammasun有关.这种台风扰动在沿海地区较强,在内陆地区较弱,其震动源在靠近台风运动路径的海底.另一种优势频率为0.1～0.18 Hz的扰动与台风无关,这种非台风扰动在地震发生前约10 h突然急剧增强,其最大值出现在地震爆发时刻.非台风扰动在靠近震中的地区较强,在沿海和西部地区较弱.震源扰动扫描算法计算初步定位的结果显示其震动源不在海底,而是分散在震中附近的内陆地区.汶川大地震前的非台风扰动是否与汶川大地震有关,值得进行更深入的研究.

The analysis of the non-typhoon-induced microseisms before the 2008 Wenchuan earthquake

To distinguish typhoon and non-typhoon effects on the tremor before the 2008-05-12 great Wenchuan earthquake, we investigate microseisms recorded by broadband seismographs in mainland of China before the earthquake. Our results indicate that the microseisms consist of two main parts that show different dynamical characters. The one in the frequency band of 0.2～0.25 Hz is related to typhoon Rammasun, which is strong near the coast of East China but weak in the inland of China, and its seismic source is located on the seabed near the track of Rammasun. The other one in the frequency band of 0.1～0.18 Hz bore no relation to Rammasun. This non-typhoon-induced microseism is strong near the epicenter of the earthquake but weak in the coast and western areas of China. Locating seismic sources of non-typhoon-induced microseism by the source scanning algorithm, we show that the sources are distributed around the epicenter of Wenchuan.