Seismic history and seismotectonics of the Sunda Arc
Seismic history and seismotectonics of the Sunda Arc
复制标题
巽他弧的地震历史和地震构造
DOI：
10.1029/jb092ib01p00421
复制
发表时间：
1987
影响因子：
--
通讯作者：
W. Mccann
中科院分区：
文献类型：
--
作者：
K. Newcomb;W. Mccann
过去 300 年的历史记录揭示了两次板间大地震（1833 年，MW = 8⁄4 1861，MW = 8⁄4–8½），导致印度尼西亚西部苏门答腊岛前弧的主要部分破裂；沿着板块边界的这一部分的板间滑动的很大一部分似乎是通过地震发生的。这些破裂带的末端与大型 (Ms ≥ 7) 和中度 (6 ≤ Ms ≤ 7) 冲击簇一致，并且与根据地质和地球物理数据推断的板块界面的不均匀性一致。 1833破裂带的北部范围与一组中、大地震、前弧内的构造拱和俯冲板块上的破裂带重合。南部部分与俯冲板块上一个非常突出的星团和一个充满沉积物的槽的沿走向延伸一致。在这项研究之前，苏门答腊岛被认为是相对抗震的，从本世纪的仪器记录中没有发生大地震推断出来。爪哇岛和小巽他群岛在历史记录中曾发生过大地震（Ms ≥ 6），但没有一次与苏门答腊岛附近发生的大地震震级相同。没有明确的证据表明爪哇前弧的冲击是板间事件，但地球物理数据表明最近海沟坡折的隆起和海沟轴线走向的变化，其中罗奥隆起的最北侧（一个突出的测深高点）似乎与前弧相互作用。该特征形成于山脊顶部，比周围的海底更有浮力，因此更难以俯冲。然而，与这种构造运动相关的地震活动并没有增加，这可能表明此时板块的结晶部分之间缺乏接触。我们推断爪哇附近板块界面上的大部分滑移是抗震发生的。沿着巽他弧发生的板间大地震的变化可以用一个模型来解释，该模型将板间耦合的变化归因于俯冲岩石圈的年龄。苏门答腊岛附近发生了板间大地震，那里最年轻的地壳年龄为 46 Ma。巽他弧的特征以及与太平洋弧的类比表明，整个苏门答腊岛都有可能产生大逆冲地震；其地震潜力应该被认为很高（因为 1833 年和 1861 年的重大事件没有再次发生）。相比之下，爪哇岛和小巽他群岛没有此类事件的报道，那里最古老的地壳年龄为 152 Ma。爪哇岛和小巽他群岛附近的板块界面应被认为具有低地震潜力。
Historic records of the last 300 years reveal two great interplate earthquakes (1833, MW = 8¾ 1861, MW = 8¼–8½), which ruptured major segments of the Sumatra fore arc in western Indonesia; a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically. The ends of these rupture zones are coincident with clusters of large (Ms ≥ 7) and moderate (6 ≤ Ms ≤ 7) shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data. The northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes, a structural arch in the fore arc, and a fracture zone on the subducted plate. The southern portion is coincident with a very prominent cluster and the along-strike extension of a sediment-filled trough on the subducted plate. Prior to this study, Sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century. Java and the Lesser Sunda Islands had major (Ms ≥ 6) earthquakes in the historic record, but none are of the same magnitude as the great events near Sumatra. There is no clear evidence that shocks in the Java fore arc were interplate events, yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the Roo Rise, a prominent bathymetrie high, appears to be interacting with the fore arc. This feature was formed at a ridge crest and is more buoyant, and thus more difficult to subduct, than the surrounding seafloor. There is no increase in seismicity associated with this tectonism, however, that may indicate a lack of contact between the crystalline portions of the plates at this time. We infer that a majority of slip on the plate interface near Java occurs aseismically. The variation in occurrence of great interplate earthquakes along the Sunda Arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere. Great interplate earthquakes occur near Sumatra, where the age of the youngest crust is 46 Ma. The characteristics of the Sunda Arc, and analogies with Pacific arcs, imply that the entire length of Sumatra has the potential to produce great thrust earthquakes; its seismic potential should be considered high (as there has been no recurrence of the great events of 1833 and 1861). In contrast, no such events have been reported off Java and the Lesser Sunda Islands, where the oldest crust is 152 Ma. The plate interface near Java and the Lesser Sunda Islands should be considered to have low seismic potential.