大同—阳高6.1级地震震源参数的确定

Determination of the Source Parameter of the Datong-Yanggao Earthquake

为计算１９８９ 年１０月１８日大同—阳高６．１级地震的震源参数，根据断裂力学的有关公式分析了断裂扩展过程中应力和位移的变化，利用弹塑性力学中的达格代尔（Ｄｕｇｄａｌｅ）模式塑性区中最大位移的公式计算了震源应力场的初始剪切应力τｏ 和地震释放的总能量ＥＴ；根据不同作者利用地震波资料和历史地震等烈度线所得出的不同震级的地震矩，利用最小二乘法拟合得出山西地区不同震级地震矩之间的关系，计算出大同—阳高６．１级地震的地震矩和其它震源参数。结果表明地震多数是在低初始应力作用下发生的（大约１００×１０５ Ｐａ左右），且与震级无关，主要决定于岩石的抗剪强度和断层面上的静摩擦力值；应力降的数值较小，大约在１０×１０５ Ｐａ～１００×１０５ Ｐａ之间，且与震级关系不大；地震释放的总能量比地震波释放的能量大一个数量级。指出利用断裂力学的有关公式计算震源应力场的初始剪切应力τｏ 和地震释放的总能量ＥＴ 在原理上是可行的，且方法简单；在缺乏地震波资料的情况下利用区域各物理量之间的统计关系计算某物理量同样是可行的，在方法上比利用地震波资料直接计算更简单。

Aaccording to formula of the rupture mechanism, the variation of stress and strain in the course of rupture expanding are analyzed in order to count the source parameter of the Datong Yanggao Earthquake, Using maximum displace formula in plasticity area of Dugdale model, the initial shearing stress (τ o) of focal stress field and total energy source energy (E T) are counted. According to different magnitude focal moment acquired by different author who use seismic wave information and seismic intensity map, the correlation of seismic moment of different magnitude in Shanxi are acquired, with least square method, the seismic moment etc. focal parameter of the Datong Yanggao Earthquake was counted. The result marked most earthquakes occur in the action of small initial stress (about 100×10 5 Pa), are irrespetive of magnitude, and are determined by rock's shearing strength and static force of friction on fault plane. The stress drop, about 10×10 5 Pa～100×10 5 Pa, is irrespective of magnitude and lass value; Total energy of earthquake is ten times as large as energy of seismic wave.That calculation of initial shearing stress (τ o) of focal stress field and total seismic energy (E T) of formula of rupture mechanism is feasible in principle. It is feasible to count these quantities in the lack of seismic wave information with regional physical quantity's statistical correlation , it is simpler than direct calculation with seismic wave.