Urgent assessment of the earthquake and tsunami hazard in western Sumatra following the 09/07 Mentawai Islands earthquake sequence.

继 09/07 明打威群岛地震序列之后，对苏门答腊岛西部的地震和海啸危险进行紧急评估。

• 批准号: NE/F012144/1
• 负责人: John McCloskey
• 金额: $ 3.68万
• 依托单位: University of Ulster
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF012144%2F1
• 关键词: Urgent; assessment; earthquake; tsunami; hazard

Starting with the great Sumatra-Andaman earthquake M=9.2 of 26 December 2004 over 2000km of the Sunda megathrust, where the Indian ocean plate is being forced under the Asian plate, has been ruptured in a series of great M>8 earthquakes. The most recent, of magnitude 8.4, occurred on 12 September 2007. Of the more than 2500km of the megathrust, from the Andaman Islands to Enganno, only 300km remains un-ruptured in the last three years. This segment, under the Island of Siberut is still capable of an earthquake of greater than magnitude 8. It has not failed since 1797, from examination of the way the earth's crust is being deformed in the area we know that it has not experienced any slow (aseismic) slip. Simple calculations, using the known rate of convergence of the plates here, show that all the strain released in 1797 has been regained and it seems clear that it is ripe for another earthquake. This could happen at any time. In addition, it is clear from earlier work and from preliminary investigation of the recent events, that the segment under Siberut is now being stressed from the north by the 2005 event and from the south by the 12/09/07 event. It is likely that such an earthquake might cause a tsunami. The maximum height of Padang, broadside on to the Siberut segment, is only 10m above sea level so a tsunami is a real threat. However, it does not have to be as destructive as the 2004 tsunami. Indeed recent work we have done, funded by NERC in 2006, has shown that the presence of the Islands offshore Padang make the threat of a massive tsunami recede significantly. Our forecasts of smaller waves generated by western Sumatran megathrust earthquakes would appear to have been borne out by preliminary data from tsunami generated by the recent M8.4 earthquake which only reached 4m in height and apparently killed no one. Recently, we have made predictions relating the height of a tsunami observed on the Sumatran Coast to the vertical movement experienced there. When one of these earthquakes occurs the offshore islands are forced upward by the earthquake while the coast of Sumatra always drops / sometimes by metres. By a detailed series of coupled earthquake and tsunami simulations we have shown that the wave height experienced onshore is directly proportional to the size of this drop. The beauty is that the size of the vertical movement can be measured up to 30 minutes before the wave arrives. The recent earthquake should allow us to test this relationship. In this project we aim to do three things. Firstly, we plan to reassess the stresses under the island of Siberut accounting for the entire earthquake sequence. These calculations, particularly the time varying components, are complex and require sophisticated computations which we will finalise during the project. Secondly, we will test the predictions of our tsunami simulation methods against data collected by the recent M8.4 event and investigate the relationship between wave height and vertical displacement. This will involve a 2 week field campaign to collect information about the wave heights near the city of Bengkulu which was hit by the recent tsunami. Scars left by the tsunami will still be clearly visible for the next couple of months and can be measured accurately in the field. Using high resolution GPS equipment, which we will borrow from the NERC Geophysical Equipment Facility, we will accurately locate the positions of wave height estimates and also measure the present height of the coast. These heights will allow us to estimate the change in height during the earthquake. Finally, we will compute another suite of tsunami scenarios taking into account the recent earthquakes and the results of our validation work. Western Sumatra is currently one of highest earthquake risk areas in the world. This project will not stop the earthquake but it will contribute to a body of scientific knowledge which will help to prepare people for it.

从2004年12月26日发生的9.2级苏门答腊-安达曼大地震开始，超过2000公里的巽他巨型逆冲断层（印度洋板块被迫压入亚洲板块之下）在一系列8级以上的大地震中发生了破裂。最近的一次震级为8.4级，发生在2007年9月12日。在从安达曼群岛到恩加诺的2500多公里的巨型逆冲断层中，只有300公里在过去三年里没有破裂。西比鲁特岛下方的这一段仍然有可能发生 8 级以上的地震。自 1797 年以来，它从未发生过故障，通过检查该地区地壳变形的方式，我们知道它没有经历过任何缓慢（地震）滑动。使用此处已知的板块收敛速度进行简单计算表明，1797 年释放的所有应变均已恢复，看来再次发生地震的时机已经成熟。这随时可能发生。此外，从早期的工作和对近期事件的初步调查可以清楚地看出，西比鲁特地区目前正受到来自北方的 2005 年事件和来自南方的 2007 年 9 月 12 日事件的压力。这样的地震很可能会引发海啸。巴东（Padang）的最大高度（西比路段的侧面）仅高于海平面 10m，因此海啸是真正的威胁。然而，它并不一定像 2004 年海啸那样具有破坏性。事实上，我们最近在 2006 年由 NERC 资助的工作表明，巴东近海岛屿的存在使得大规模海啸的威胁显着减弱。我们对苏门答腊岛西部巨型逆冲地震产生较小波浪的预测似乎已被最近发生的 M8.4 地震产生的海啸的初步数据所证实，这次地震的高度仅达到 4 m，显然没有造成人员死亡。最近，我们做出了将苏门答腊海岸观测到的海啸高度与那里经历的垂直运动联系起来的预测。当其中一场地震发生时，近海岛屿会因地震而向上移动，而苏门答腊岛的海岸总是下降（有时下降数米）。通过一系列详细的地震和海啸耦合模拟，我们表明岸上经历的波高与落差的大小成正比。美妙之处在于，可以在海浪到来前 30 分钟测量垂直运动的大小。最近的地震应该让我们检验这种关系。在这个项目中，我们的目标是做三件事。首先，我们计划重新评估西比路岛下方整个地震序列的应力。这些计算，特别是随时间变化的分量，很复杂，需要复杂的计算，我们将在项目期间完成这些计算。其次，我们将根据最近的 M8.4 事件收集的数据来测试我们的海啸模拟方法的预测，并研究波高和垂直位移之间的关系。这将涉及为期两周的实地活动，收集有关最近遭受海啸袭击的明古鲁市附近波浪高度的信息。在接下来的几个月里，海啸留下的伤痕仍然清晰可见，并且可以在现场准确测量。使用我们从 NERC 地球物理设备设施借来的高分辨率 GPS 设备，我们将准确定位波高估计的位置，并测量海岸的当前高度。这些高度将使我们能够估计地震期间高度的变化。最后，我们将考虑最近的地震和验证工作的结果，计算另一套海啸情景。西苏门答腊岛目前是世界上地震风险最高的地区之一。该项目不会阻止地震，但它将有助于积累科学知识，帮助人们做好应对地震的准备。

项目成果

Interseismic coupling, stress evolution, and earthquake slip on the Sunda megathrust

• DOI: 10.1002/grl.50776
• 发表时间: 2013-08
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: S. Nalbant;J. McCloskey;S. Steacy;M. Nicbhloscaidh;S. Murphy

Using a genetic algorithm to estimate the details of earthquake slip distributions from point surface displacements

使用遗传算法从点面位移估计地震滑动分布的细节

• DOI: 10.1002/2015jb012181
• 发表时间: 2016
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Lindsay A