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2011年12月14日在日本歧阜县瑞浪市之下的菲律宾海板块(PHS)发生了M5.6地震。东浓地震科学研究所(TRIES)的密集地震台网观测到了美浓东部之下的该地震及震中周围余震中的17次。我们详细研究了这些地震事件的分布和震源机制,讨论了菲律宾海板块和俯冲构造内的应力场。在初震(M1.6,震源深度48.1km)之后,在菲律宾海板块上界面之下约6km发生了主震(M5.6,震源深度47.7km)。这次地震的余震活动在54°东倾的平面上向下扩展到洋底莫霍面附近。多数地震的震源机制具有正断型特征,T轴为东西(与海沟轴平行)方向。我们认为,菲律宾海板块的凸面向下形状和平行于海沟轴的拉张状态的应力场,可能是这些正断型地震的诱因。
December 14, 2011 The M5.6 earthquake struck the Philippine Sea Plate (PHS) under Raumang, Gifu Prefecture, Japan. The Dense Seismic Network of the East Consensus Earthquake Research Institute (TRIES) has observed 17 of the earthquakes and the aftershocks around the epicenter beneath the eastern Mino. We studied in detail the distribution and source mechanisms of these seismogenic events and discussed the stress fields within the Philippine Sea plate and subduction structures. After the initial earthquake (M1.6, focal depth 48.1km), the main shock (M5.6, focal depth 47.7km) occurred about 6km below the upper interface of the Philippine Sea plate. The aftershock activity of this earthquake extended downwards to a depth of 54 ° near the ocean floor near the Moho. Most earthquakes have normal faulting features and the T-axis is east-west (parallel to the trench axis). We believe that the convex downward shape of the Philippine Sea plate and the stress field parallel to the tension axis of the trench axis may be the inducement of these normal-fault earthquakes.