Seismic rupture associated with subduction of the Cocos Ridge
Seismic rupture associated with subduction of the Cocos Ridge
复制标题
与科科斯海岭俯冲相关的地震破裂
DOI：
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
D. Wiens
中科院分区：
文献类型：
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作者：
S. Adamek;F. Tajima;D. Wiens
1983 年 4 月 3 日，哥斯达黎加地震（Mw = 7.4，Ms = 7.3）发生在抗震科科斯海岭部分俯冲到加勒比板块之下的地方。震中位于70×110平方公里的初始余震区的东部边缘，随后该区出现了相当大的扩展。 P波方向性分析表明，破裂前沿从震中向西传播了63 km，到达主力矩释放被截断的位置。发生在同一震中区的 1941 年事件（Ms = 7.5）的震源时程似乎与 1983 年事件相似，但复杂性更高，力矩释放启动更慢。 1983 年事件的低应力降（2-3 巴）和地震滑移与构造滑移之比较低（1983 年事件为 0.15）表明下降板片与上覆板块之间的耦合较弱。然而，1904年、1941年和1983年的事件暗示该区域大事件（mag > 7.0）的复发时间约为40年，这表明科科斯海岭导致与邻近俯冲带相比增加的部分耦合。缓慢的源破裂过程可能反映了哥斯达黎加弧与浮力科科斯海脊附近的俯冲板块之间接触区域的性质。 1979 年 7 月 1 日的正常断层事件 (mb = 5.3) 与现今布里卡半岛的隆起一致，之前的研究表明这与科科斯海岭的俯冲有关。布里卡和奥萨半岛可能表现为独立块体，影响余震扩展模式中反映的部分耦合分布。
The April 3,1983, Costa Rica earthquake (Mw = 7.4, Ms = 7.3) occurred where the aseismic Cocos Ridge has been partially subducting beneath the Caribbean plate. The epicenter is at the eastern edge of the 70 × 110 km² initial aftershock area, which later shows considerable expansion. P wave directivity analysis indicates that the rupture front propagated westward 63 km from the epicenter to where the major moment release was truncated. The source time history of the 1941 event (Ms = 7.5) which occurred in the same epicentral area appears to be similar to the 1983 event but with more complexity and a slower initiation of moment release. The low stress drop of the 1983 event, 2–3 bar, and low ratio of seismic slip to tectonic slip, 0.15 for the 1983 event, suggest that the coupling between the descending slab and the overlying plate is weak. Yet, a recurrence time for large events (mag > 7.0) in this zone of about 40 years is implied by the 1904, 1941, and 1983 events, suggesting that the Cocos Ridge causes increased partial coupling compared with that in the adjacent subduction zone. The slow source rupture process may reflect the nature of the contact area between the Costa Rica arc and the subducting plate in the vicinity of the bouyant Cocos Ridge. The normal faulting event of July 1, 1979, (mb = 5.3) is consistent with present-day uplift of the Burica Peninsula, which previous studies suggest is related to the subduction of the Cocos Ridge. The Burica and Osa peninsulas may behave as detached blocks which influence the distribution of partial coupling reflected in the aftershock expansion pattern.