Paleoseismic Investigation of the Aksay Restraining Double Bend, Altyn Tagh Fault, and Its Implication for Barrier‐Breaching Ruptures
Paleoseismic Investigation of the Aksay Restraining Double Bend, Altyn Tagh Fault, and Its Implication for Barrier‐Breaching Ruptures
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DOI：
10.1029/2017jb015397
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发表时间：
2018-05
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通讯作者：
Y. Shao;J. Liu-zeng;M. Oskin;A. Elliott;Peng Wang;Jinyu Zhang;Zhaode Yuan;Zhanfei Li
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文献类型：
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作者：
Y. Shao;J. Liu-zeng;M. Oskin;A. Elliott;Peng Wang;Jinyu Zhang;Zhaode Yuan;Zhanfei Li
断层几何形状被认为是对地震破裂程度、震级和复发行为的重要控制。然而，多周期地震破裂模拟表明，几何障碍并不总是阻止破裂传播。先前多次地震产生的应力积累可能会导致屏障偶尔破裂，从而产生更大的破裂。在这里，我们提供了来自阿克赛限制阿尔金断层双弯的古地震数据，这些数据支持了这种破坏。阿克赛弯曲由两条主链组成，它们以宽阔的压弯结构弯曲在一起。我们研究了两条地震带的古地震历史，以评估弯曲内和弯曲外事件的相关性。南岸有四次很可能发生的古地震，平均间隔为 1,433 ± 57 年，变异系数 (COV) 约为 0.5。北岸记录了公纪前 3650 年之后的四个最高质量事件，平均间隔约为 1,326 ± 179 年，COV 约为 0.3。不同的复发间隔和相对较高的 COV 表明阿克赛弯曲内的断层仅具有准周期性破裂复发。比较事件序列也表明了复杂的破裂历史。倒数第二个事件似乎与整个弯曲区以及之前发布的东部和西部古地震年表相关，这支持它是一次突破障碍事件。这里报告的事件历史表明，多次地震必须在几个地震周期内终止于弯曲内，以便达到适合地震破裂的应力条件。
Fault geometry is recognized as an important control on earthquake rupture extent, magnitude, and recurrence behavior. However, multicycle earthquake rupture simulations indicate that geometrical barriers do not always stop rupture propagation. Stress buildup over multiple prior earthquakes may promote an occasional breach of a barrier, producing a significantly larger rupture. Here we present paleoseismic data from the Aksay restraining double bend of the Altyn Tagh fault, which supports such breaching. The Aksay bend consists of two main strands, which bend together in a broad transpressional configuration. We investigate the paleo‐earthquake histories of both strands to assess the correlation of events within and beyond the bend. The south strand exhibits four very likely paleo‐earthquakes with an average interval of 1,433 ± 57 years and a coefficient of variation (COV) of ~ 0.5. The north strand records four highest‐quality events after 3650 Before Common Era with an average interval of ~1,326 ± 179 years and a COV of ~0.3. The varying recurrence intervals and relatively high COVs indicate that faults within the Aksay bend have only quasi‐periodic rupture recurrence. Comparing the event sequences also suggests a complex rupture history. The penultimate event appears to correlate across the bend, as well as to previously published paleoseismic chronologies both to the east and to the west, which supports it being a barrier‐breaching event. The event histories reported here indicate that multiple earthquakes must terminate within the bend, over several earthquake cycles, in order to arrive at a stress condition suitable for a breaching earthquake rupture.