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yexuqing木虫之王 (文学泰斗)
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海洋转换断层的结构性破裂屏障导致可预测的地震周期
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Predictable seismic cycles result from structural rupture barriers on oceanic transform faults 海洋转换断层的结构性破裂屏障导致可预测的地震周期 ▲ 作者：JIANHUA GONG, WENYUAN FAN, JEFFREY J. MCGUIRE, MARK D. BEHN, JESSICA M. WARREN, EMILY ROLAND, ET AL. ▲链接： https://www.science.org/doi/10.1126/science.ady6190 ▲ 摘要：海洋转换断层（OTFs）上发生的震级大于5.5级的地震，会反复破坏同一锁定区域，有时呈现准周期性。这些区域被阻止地震传播的“屏障”分隔开，且其滑动主要以无震形式进行。然而，控制这一系统性行为的物理过程尚不清楚。 研究组分析了戈法尔转换断层沿线的两个屏障，其在过去三十年中阻止了约15次6级地震。海底地震仪数据表明，这些屏障在主震前存在强烈的微地震活动，包括多股断层和横向偏移100至400米的张扭性阶区。 这些特征与那些依赖速度强化摩擦或大几何阶跃的地震破裂终止模型相矛盾，反而指向了损伤增强的孔隙度和剪胀强化机制。通过隔离破裂段，这些屏障调控着OTF地震的准周期性重现。 ▲ Abstract：Earthquakes of magnitude (M) >5.5 on oceanic transform faults (OTFs) repeatedly rupture the same locked patches, sometimes quasiperiodically. These patches are separated by “barriers” that halt earthquake propagation and slip mostly aseismically. However, the physical processes governing this systematic behavior remain unclear. We analyzed two barriers along the Gofar transform fault that have arrested ~15 M6 earthquakes over the past three decades. Ocean bottom seismometer data indicate that the barriers hosted intense microseismicity before the mainshocks and comprise multistrand faults and transtensional stepovers with 100- to 400-m lateral offset. These characteristics contradict earthquake rupture termination models invoking velocity-strengthening friction or large geometric steps and instead point to damage-enhanced porosity and dilatancy-strengthening mechanisms. By isolating rupture segments, the barriers regulate the quasiperiodic recurrence of OTF earthquakes. |
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