Collaborative Research: Near-Field Observations of Preseismic, Coseismic, and Postseismic Slip on the Northern Costa Rica Megathrust

合作研究：哥斯达黎加北部巨型逆冲断层的震前、同震和震后滑动的近场观测

• 批准号: 1321552
• 负责人: Zhigang Peng
• 金额: $ 14.06万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321552&HistoricalAwards=false
• 关键词: Collaborative; Research; Near; Field; Observations

The plate boundary at convergent margins produces most of the world?s largest earthquakes, threatening local inhabitants and global populations through destructive shaking and tsunami generation. An Mw 7.6 earthquake occurred on 5 September 2012 in Nicoya Peninsula, northern Costa Rica directly beneath a network of seismic and continuous GPS stations. It provides a unique opportunity to study the cycle of a megathrust earthquake in unprecedented detail. This project seeks to better understand the preparation process of megathrust earthquakes by identifying slow preslip and/or patterns in foreshock activity, and evolutions of aftershocks and afterslip induced by the mainshock. Our project has important implications for predictability of large earthquakes, the potential size of the megathrust earthquake, the strong ground motions and associated damage, and tectonic strain accumulation and release during an earthquake cycle. Major research questions to be addressed include whether there is discernible preparation activity before the mainshock, if distinct regions of the plate boundary host coseismic versus slow and after slip, if slip in the mainshock occurs in regions accumulating strain during the interseismic period, whether aftershocks are driven by afterslip or other processes, and what effect mainshock rupture has on seismic velocities and properties of the plate interface. Because we have been measuring surface deformation and seismicity directly above the megathrust for over a decade preceding the 2012 Nicoya earthquake, we can compare the distribution of coseismic slip with the interseismic strain accumulation pattern, slow slip behavior, and precursory seismicity and address all of these questions in a single location. To ascertain whether any accelerating foreshock activity and aftershock expansion/migration occurs, a complete catalog of seismic activity before and after the mainshock is required. We will use all earthquakes in our existing catalog as templates and scan through continuous records to identify additional events easily missed by automated detection algorithms and visual inspection. Event pairs with the highest correlation coefficients will be grouped into repeating earthquake clusters and used to infer slow-slip and afterslip, and track temporal changes of subduction zone interface properties. We will also detect tectonic tremor long before and after the mainshock and use it as a proxy for slow slip and investigate whether tremor/slow slip events occur before major earthquakes. Finally, we will compare high-resolution co-seismic slip with aseismic slip during postseismic and interseismic period as well as microseismicity to understand different frictional properties of the plate interface. Because of the high-quality data collected over the past decade, and the close proximity to the megathrust, our project could lead to significant advances on how subduction zone properties evolve immediate before and after a major megathrust event.

融合边缘的板界产生了世界上大部分地区最大的地震，威胁着当地居民和全球人口。 MW 7.6地震发生在2012年9月5日，直接在哥斯达黎加北部的尼科亚半岛，直接在地震和连续的GPS站网络下方。它提供了一个独特的机会，可以以前所未有的细节研究大型地震的周期。该项目旨在通过识别前期活动中的慢速前后和/或模式，以及由主震动引起的余震和余后的进化，以更好地理解大型地震的制备过程。我们的项目对大地震的可预测性，大地震的潜在大小，强烈的地面运动和相关损害以及构造应变的积累和释放在地震周期中具有重要意义。要解决的主要研究问题包括在主震前是否有可辨别的准备活动，如果板边界宿主的不同区域coseiss cososic vers slip and slip slip s slip and slip s slip and slip s slip，如果在主震中发生在经济震动期间积累的区域，是否会在次震动期间积累压力，是否由余垫驱动。由于我们一直在2012年尼科亚（Nicoya）地震之前的十多年来测量直接在大型上方的表面变形和地震性，因此我们可以将coseismic滑移的分布与跨性菌株的积累模式，慢速滑移行为，慢速滑移行为以及术前的地震性以及在单个位置中的所有这些问题的所有问题。为了确定是否发生任何加速前换活动和余震膨胀/迁移，需要在需要前后和之后的地震活动目录。我们将使用现有目录中的所有地震作为模板，并通过连续记录进行扫描，以确定自动检测算法和视觉检查容易错过的其他事件。具有最高相关系数的事件对将分组为重复地震簇，并用于推断慢滑层和后滑动后，并跟踪俯冲区界面特性的时间变化。我们还将在主震前和之后发现构造震颤，并将其用作缓慢滑移的代理，并研究震颤/慢速事件是否发生在大地震之前。最后，我们将比较高分辨率的共和性滑移与地震后和微观期间的无性滑移以及微吸收性，以了解板界面的不同摩擦特性。由于过去十年收集的高质量数据以及与Megathrust的近距离，我们的项目可能会在俯冲区的属性如何进化之前和之后的重大巨型事件发生后立即发展。