The Bucaramanga Nest: A Natural Laboratory for Exploring the Mechanics of Intermediate Depth Earthquakes

布卡拉曼加巢：探索中深度地震力学的天然实验室

• 批准号: 1045684
• 负责人: Gregory Beroza
• 金额: $ 26.76万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-15 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045684&HistoricalAwards=false
• 关键词: Bucaramanga; Nest; Natural; Laboratory; Exploring

Most earthquakes occur in the Earth's shallow crust, but some are located at greater depth. These intermediate-depth earthquakes occur in the crust and upper mantle of tectonic plates that are subducting into the deep Earth at collisional plate boundaries. Beyond this, we lack an understanding of why these earthquakes occur at some places (e.g., Colombia, Afghanistan, Romania, northern Cascadia), but not at other, seemingly similar, collisional plate boundaries. We also lack a model that explains their recurrence, i.e., why they occur when they do. While not as deadly as shallow earthquakes, intermediate-depth earthquakes can occasionally be devastating. For example, the 1939 Chillan, Chile intermediate-depth earthquake killed ~28,000 people, and is by far the deadliest earthquake in that country's history. Intermediate-depth earthquakes can also be quite damaging. For example, the 2001 Nisqually, Washington earthquake caused over $2 billion in losses, despite being located on the southern fringe of metropolitan Seattle. The focus of this study is the intense "nest" of intermediate-depth earthquakes under Bucaramanga, Colombia. This area hosts the greatest concentration of intermediate-depth earthquakes in the world, and their frequent occurrence means that this presents the best opportunity in the world to study them. By using data from the state-of-the-art Colombian National Seismic Network, we will gain a deeper understanding into how these earthquakes work. Although he will be supported with funding from his own institution, this project will help build collaborations between Colombia and the US. It will also help develop capacity for earthquake monitoring and evaluation in the developing world. The understanding of intermediate-depth earthquakes that we develop should be broadly applicable to similar earthquakes worldwide, including the Pacific Northwest of the US.This three-year project, to be carried out in collaboration with Professor German Prieto of the University of the Andes in Bogota, Colombia, will study the intense concentration of intermediate-depth earthquakes under Bucaramanga, Colombia using state-of-the-art analysis of waveform data from the Colombian National Seismic network. We will use cross-correlation-based measurements to develop: precise earthquake locations, improved 3D velocity structure, and more accurate source parameter estimates of these events. The result will be a better understanding of earthquakes in the Bucaramanga Nest in particular, and intermediate-depth earthquakes in general. Among the questions we will address are: Do these earthquakes occur due to collision of the Caribbean and Nazca Plates at depth? Do they occur on discernable fault planes or are they diffuse throughought the subducting slab? Are there Vp/Vs anomalies that might indicate a role for pore fluids in their occurence? How do the source properties of intermediate-depth earthquakes vary with earthquake size? Can we identify repeating earthquakes, and if so, is their recurrence non-Poissonian (i.e., not random in time, but governed by a physically motivated process like elastic rebound)? What controls the maximum size of intermediate-depth earthquakes under Bucaramanga? How can the results of our study be used to place useful constraints on the size and recurrence of intermediate-depth earthquakes around the world that will be useful for hazard characterization?This project is supported by the Geophysics Program and the Colombia Program of the Office of International Science and Engineering.

大多数地震发生在地球的浅层地壳中，但有些地震位于更深的深度。 这些中等深度的地震发生在构造板的地壳和上层，它们正俯冲到碰撞板边界的深地球上。 除此之外，我们还不了解这些地震为何在某些地方（例如哥伦比亚，阿富汗，罗马尼亚，卡斯卡迪亚北部）发生，但在其他看似相似的碰撞板界边界并不了解。 我们还缺少一个解释其复发的模型，即它们在这样做时发生的原因。 虽然中间地震虽然不如浅层地震，但偶尔会造成毁灭性的地震。 例如，1939年的辣椒，智利中级严重地震造成约28,000人丧生，这是该国历史上最致命的地震。 中级严重的地震也可能是相当破坏性的。 例如，尽管位于西雅图大都会的南部边缘，但华盛顿地震是2001年的尼斯（Nisqually），造成了超过20亿美元的损失。 这项研究的重点是哥伦比亚Bucaramanga领导下中期地震的强烈“巢”。 该地区拥有世界上最严重的深度地震集中，它们的频繁发生意味着这是世界上最好的机会进行研究。 通过使用最先进的哥伦比亚国家地震网络的数据，我们将对这些地震的运作方式有更深入的了解。 尽管他将获得自己机构的资助，但该项目将有助于建立哥伦比亚与美国之间的合作。 它还将有助于发展发展中国家地震监测和评估的能力。 对我们开发的中等深度地震的理解应广泛适用于全球类似地震，包括美国的西北太平洋地区。这三年的项目将与波哥巴安第斯山脉的德国普里托教授合作进行，哥伦比亚的安第斯山脉教授将研究哥伦比亚群岛的强化范围，以研究哥伦比亚群岛的强化范围 - 伯加拉姆境内的繁殖范围 - 来自哥伦比亚国家地震网络。 我们将使用基于互相关的测量来开发：精确的地震位置，改进的3D速度结构以及这些事件的更准确的源参数估计。 结果将是对Bucaramanga巢中的地震的更好理解，并且总体上是中等深度地震。 我们将要解决的问题包括：这些地震是否由于加勒比海和纳斯卡板的碰撞而发生？ 它们是在可辨别的断层平面上发生的还是通过俯冲平板扩散的？ 是否存在VP/VS异常，可能表明孔流体在其发生中的作用？ 中间严重地震的源特性如何随地震大小而变化？ 我们可以确定重复地震，如果是这样，他们的复发是非波斯顿人（即，不是随着时间的时间，而是受弹性反弹之类的自然动机过程）的？ 是什么控制了Bucaramanga下中期地震的最大大小？ 我们的研究结果如何用于对世界各地中等深度地震的大小和复发，对危害表征有用？该项目得到地球物理学计划和国际科学和工程办公室的哥伦比亚计划的支持。