Collaborative research: A study of transient aseismic slip and non-volcanic tremor in southern Mexico with large aperture seismic and GPS arrays

合作研究：利用大孔径地震和GPS阵列研究墨西哥南部瞬态地震滑移和非火山地震

• 批准号: 0510887
• 负责人: Dennis DeMets
• 金额: $ 16.57万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0510887&HistoricalAwards=false
• 关键词: Collaborative; research; study; transient; aseismic

Intellectural merit: Funds are requested for a joint geodetic and seismic study ofthe Oaxaca-Guerrero segment of the Middle America subduction zone, one of the few placeson earth where land-based GPS and seismic observations can be used to study both thelocked, seismogenic area of a subduction interface and region of deeper transitionalslip, where episodic tremor and slip may originate. The principal scientific goal isto better understand the recently discovered phenomenon of episodic slip transientsand its role in either relieving or increasing strain accumulating along the seismogenicportion of a subduction interface. A pilot study during the past year shows that suchtransients are occurring as frequently as every 12-24 months in this region, thatsome transients (1998 and 2004) originate far outside the Guerrero seismic gap, andthat the transients may be accompanied by non-volcanic seismic tremors. Based on thesepreviously unrecognized results, deployment for 24 months of an 8-station broadbandseismic array and expansion of a regional continuous GPS array to include 4 criticallylocated stations in a region where the transients appear to occur are planned. Thenew seismic array, which will span abroad gap between two dense seismic transects being installed as part of the alreadyfunded Caltech/UNAM Middle America Seismic Experiment, will allow detection and locationof any episodic tremors in the study area. Continuous GPS measurements from thepre-existing GPS stations and nine new stations constructed by this group andcollaborator Enrique Cabral of UNAM will provide critical complementary informationabout the source regions, magnitude, and timing of episodic slip. Data from an existingsmaller-footprint 30-station continuous and campaign GPS array that DeMets and Cabraloperate in Oaxaca above the Cocos-North America subduction interface will also be usedto study in more detail deformation within a conspicuous seismic gap analogous to,but smaller than the well-known Guerrero seismic gap. The combined GPS and seismicarrays will be a powerful tool for studying subduction transients and non-volcanictremor, and for imaging spatial and temporal variations in frictional couplingalong the locked and transitional zones beneath our network. Brudzinski, who will bea new faculty member at Miami University of Ohio in August of 2005, will purchase thenecessary seismic equipment with start-up funds from his faculty position and willhave it prepared for a two-year deployment in early 2006. DeMets at UW-Madison willcoordinate the GPS station installation with Dr. Cabral, as well as a modest expansionof the Oaxaca GPS network to improve coverage of the aforementioned seismic gap. TheUW-Madison geophysics group has a long history of deploying seismic and GPS networksand will provide at no cost two expert technicians to help build and maintain thecombined seismic and GPS network. Responsibilities for modeling of the geodetic andseismic observations will lie respectively with DeMets and Brudzinski.Broader impacts: Episodic tremor and slip are a newly observed phenomenon that appearsto be related to many different aspects of earth science (seismology, tectonics,petrology, and geodynamics), with possible ramifications for understanding triggeringof megathrust earthquakes. Students at Miami University will be offered a unique opportunityto participate in a field workshop course that will coincide with the initial seismicdeployment, thereby exposing students to a geophysics field research. Broader impacts atUW-Madison will include education of Mexican graduate student Francisco Correa-Mora,who will do a substantial portion of his dissertation research on the mechanics ofsubduction along the Middle America trench. The availability of new continuous andcampaign GPS and seismic data to the broader geophysical community will alsoextend the impact of this work beyond our group, particularly once future transientslip episodes and/or tremor sequences are recorded.

学术价值：请求资金对中美洲俯冲带的瓦哈卡-格雷罗段进行联合大地测量和地震研究，该区域是地球上少数几个可以使用陆基 GPS 和地震观测来研究俯冲界面的锁定发震区域和可能产生阵发性震颤和滑动的更深过渡滑移区域的地方之一。主要的科学目标是更好地了解最近发现的幕式滑移瞬变现象及其在减轻或增加沿俯冲界面震源部分累积的应变方面的作用。去年的一项试点研究表明，此类瞬变在该地区每 12-24 个月就会发生一次，一些瞬变（1998 年和 2004 年）起源于格雷罗地震间隙之外，并且瞬变可能伴随着非火山地震。 基于这些以前未被认识到的结果，计划部署一个为期 24 个月的 8 站宽带地震阵列，并扩展一个区域连续 GPS 阵列，以包括瞬变似乎发生的区域中的 4 个关键位置的地震台。新的地震阵列将跨越两个密集地震横断面之间的间隙，作为已资助的加州理工学院/墨西哥国立自治大学中美洲地震实验的一部分安装，将允许检测和定位研究区域的任何阵发性地震。该小组与墨西哥国立自治大学的合作者恩里克·卡布拉尔 (Enrique Cabral) 对现有 GPS 站和九个新站进行的连续 GPS 测量将提供有关间歇性滑移的源区、幅度和时间的重要补充信息。 DeMets 和 Cabral 在瓦哈卡州科科斯-北美俯冲界面上方运行的现有小型 30 站连续活动 GPS 阵列的数据也将用于更详细地研究类似于但小于著名的格雷罗地震间隙的显着地震间隙内的变形。 GPS 和地震阵列相结合将成为研究俯冲瞬变和非火山地震以及对沿我们网络下方锁定和过渡带的摩擦耦合的空间和时间变化进行成像的强大工具。布鲁津斯基 (Brudzinski) 将于 2005 年 8 月成为俄亥俄州迈阿密大学的新教员，他将利用其教职的启动资金购买必要的地震设备，并准备在 2006 年初进行为期两年的部署。威斯康星大学麦迪逊分校的 DeMet 将与卡布拉尔博士协调 GPS 站的安装，并适度扩展瓦哈卡 GPS 网络，以改善上述设备的覆盖范围 地震间隙。威斯康辛大学麦迪逊分校地球物理小组在部署地震和 GPS 网络方面拥有悠久的历史，并将免费提供两名专家技术人员来帮助建立和维护地震和 GPS 网络。 DeMet 和 Brudzinski 分别负责大地测量和地震观测的建模。 更广泛的影响：阵发性震颤和滑动是一种新观察到的现象，似乎与地球科学的许多不同方面（地震学、构造学、岩石学和地球动力学）有关，可能对理解特大逆冲地震的触发产生影响。迈阿密大学的学生将有一个独特的机会参加现场研讨会课程，该课程将与最初的地震部署同时进行，从而使学生接触到地球物理学现场研究。威斯康星大学麦迪逊分校更广泛的影响将包括墨西哥研究生弗朗西斯科·科雷亚·莫拉的教育，他的论文研究的很大一部分是关于中美洲海沟的俯冲力学。新的连续和活动 GPS 和地震数据向更广泛的地球物理界的可用性也将使这项工作的影响超出我们的小组，特别是一旦记录了未来的瞬态滑移事件和/或地震序列。