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1989年12月25日在昂加瓦半岛发生了一次6.3级地震,这是魁北克北部地区至少60年来最大的一次事件,是北美东部历史地震中唯一被证实产生了地表破裂的地震。野外观测表明,该地震为逆断层和走滑断层运动的组合。波形模拟表明这次地震由两个子事件组成,开始是沿东北—西南走向的逆断层事件、随后是一次更大一点的沿北北东—南南西走向的走滑子事件。面波等效双力偶矩1.3×10~(25)dyne-cm(ldyn=10~(-5)N),两个子事件的矩比单个子事件矩几乎大一倍。子事件的深度都是3km,时间上相差0.9s,第二个子事件位于第一个子事件西南5.2km。波形模拟测定的震源参数和由地面观测导出的结果大体符合,但子事件断错上有些差别,如果走滑运动分布在破裂西南端的几条小规模断层上,或者没有发现完整的地面破裂,也许差别就不存在了。由断层面解推测的应力方向与加拿大北部地区大多数地震机制一致。昂加瓦地震和其他大陆板内地震一样,震源浅而复杂,且发生在早先尚未破裂的断层上。
An earthquake measuring 6.3 on the Angwava Peninsula on December 25, 1989, the largest such event in northern Québec in at least 60 years, was the only one that confirmed the occurrence of a surface rupture in the historic North East United States. Field observations show that the earthquake is a combination of thrust and strike-slip faults. Waveform simulations show that the earthquake consists of two sub-events, beginning with an inverse fault strike along the northeast-southwest course, followed by a larger strike-slip event along north, north, east, south, west and west. The equivalent twin moment of surface wave is 1.3 × 10 ~ (25) dyne-cm (ldyn = 10 ~ (-5) N). The moments of two sub-events are almost twice as large as that of a single sub-event. The sub-events are all 3km in depth with a time difference of 0.9s. The second sub-event is located 5.2km southwest of the first sub-event. The source parameters determined by the waveform simulations generally agree with those derived from the surface observations. However, there are some differences between sub-event faults. If the strike-slip motion is distributed on several small faults on the southwestern part of the rupture, or if no complete surface rupture is found, The difference does not exist. The stress directions deduced from fault plane solutions are consistent with most of the seismic mechanisms in northern Canada. Like the other inland intra-earthquakes, the Anghawa earthquake was shallow and complex and occurred on a previously unbroken fault.