本文根据近震源条件下,由北京数字遥测地震台网观测到的波形资料,利用Brune模式,得到了2002年1月至2006年6月期间首都圈及邻近地区989次ML≥2.0地震的震源谱,测定了它们的拐角频率和零频幅值.通过相关计算公式,得到了破裂半径、地震矩、地震能量、应力降、视应力等震源动力学参数.分析了这些动力学参数的标度关系以及在2006年7月4日河北文安MS5.1地震前的时空变化特征.结果表明,文安MS5.1地震前,视应力、应力降、地震能量与破裂半径比等出现了相对高值集中区,这些高值集中区主要分布在华北平原带上；从时间变化曲线可以看出,文安MS5.1地震前华北平原带上视应力、应力降、地震能量与破裂半径比等参数都表现出了明显的升高变化过程,而拐角频率则显示出趋势性下降变化特征.这可能与文安MS5.1地震前华北平原带上应力的增强过程有关.%Based on near-source conditions, we used waveform data observed by the Beijing Digital Telemetry Seismic Network and obtained source spectrum, corner frequency and zero frequency amplitude values of 989 earthquakes with magnitude larger than ML2. 0 occurred in the capital circle of China and surrounding area from January 2002 to June 2006 by the Brune model. Some relevant formulas had been used for calculation of a few focal dynamic parameters, such as rupture radius, seismic moment, seismic energy, stress drop, apparent stress, and so on. The scaling relations of these dynamic parameters and characters of the temporal-spatial variations before the Wen'an MS5. 1 earthquake in Hebei Province of July 20, 2006 had been analyzed. Results show that apparent stress, stress drop, seismic energy and rupture radius ratio appeared relatively high in some focus areas before the Wen'an MS5. 1 earthquake. These areas were mainly distributed in the North China Plain. It could be seen from the time curves that apparent stress, stress drop, seismic energy and rupture radius ratio and other parameters had shown a significant increasing process before the Wen'an MS5. 1 earthquake, but corner frequency showed a trend of decreased variation. This result might be related to the increasing process of stress in the North China Plain before the Wen'an MS5. 1 earthquake.
展开▼
