CAREER: Integrated Study of Shallow Subduction Seismogenesis and Locking Along the Middle America Trench

在最大的巨型逆冲断层和海啸地震中，控制浅界面耦合和近海沟地震破裂的过程知之甚少。为维持这些事件而积累的地震耦合量是高度可变的。因此，我们不能简单地定义地震的震级和复发率。此外，耦合变化显着沿着俯冲带，与破裂的锁定补丁具有不同的影响，这是科学上的重要性和社会相关的。在罕见的事件中，如2006年的爪哇地震，界面最浅的部分会破裂，导致海啸的可能性急剧增加。 这些事件，被称为？海啸地震？是神秘的，因为控制浅层地震孕育锁定的过程知之甚少。 这项研究将照亮锁定沿着的巨型逆冲断层区通过检查观测锁定，过去的大地震，目前的小地震，和变化之间的关系沿着俯冲界面。之所以选择北方哥斯达黎加和尼加拉瓜地区，是因为这些地区有丰富的数据，最近发生了一次罕见的海啸地震，而且陆地与孕震界面异常接近。该项目将是一个为期五年的努力，整合地震，大地测量和建模结果，利用各种地球物理工具，其中纽曼的专业知识。为此，他将在2010年开展一项新的活动，改进区域GPS速度场;他将结合联合收割机现有的地震数据集、地震层析成像和剖面，沿着新的事件，开发一个连续的板块界面模型。他将利用地震活动性对地震率分布的空间和时间变化进行最先进的分析，并确定其作为锁定代理的有效性。如果得到确认，该工具将用于确定尼加拉瓜近海最近发生大海啸地震的地区和全球定位系统无法分辨的孕震界面的这种特征变化。2）探索整个孕震区地震率的震间变化，用于了解活动性、应力和观测到的无震滑动的区域和时间变化; 3）检查大界面地震的历史，以确定耦合的区域变化; 4）建立新的区域性GPS震间收敛速度场，并识别任何短暂的长周期收敛时间特征。这项研究将在哥斯达黎加正在进行的12个台站地震阵列的基础上进行，其中包括格鲁吉亚科技公司拥有的四个宽带地震仪，并将与该区域正在进行的连续全球定位系统网络合作进行。将使用地震定义的界面对结果进行建模，并将锁定结果与地震活动率绘图进行比较，以进一步确定该区域的空间和时间变化。如果验证作为一个独特的代理界面应力，地震率（b值）映射将是有用的，有效地确定锁定区在近海地区，大地测量技术目前非常昂贵，较少使用。更广泛的影响：该项目将提高我们的理解浅俯冲地震成因和海啸灾害的机械控制，具有直接的社会效益。两名格鲁吉亚理工学院的研究生将得到这个项目的支持，在那里他们将接受培训，通过论文和演讲进行研究和传播成果。该项目将支持哥斯达黎加的科学培训和基础设施。PI是一个开始的调查员，该项目将有助于在格鲁吉亚理工学院建立一个动态的物理学研究小组。通过该项目获得的知识将被纳入格鲁吉亚理工学院的课程。 该计划将开发一个格鲁吉亚教育地震网络，该网络将与学习模块一起使用，以加强格鲁吉亚学校的地球科学课程。 该计划覆盖的学校将包括不同社会经济群体的学生，最初的目标学校是亚特兰大市中心附近的一所特许学校，主要是低收入和少数民族学生。

The processes that control shallow interface coupling, and near-trench earthquake rupture, in both the largest megathrust and tsunami earthquakes, are poorly understood. The amount of seismic coupling that builds up to sustain these events is highly variable. Thus, we cannot simply define the magnitude and rate of recurrence of earthquakes. Additionally, coupling changes dramatically along subduction zones, with rupture of locked patches having diverse effects that are both scientifically important and societally relevant. In rare events, such as the Java 2006 earthquake, the shallowest portion of the interface fails, causing dramatically increased tsunami potential. These events, called ?tsunami earthquakes?, are enigmatic because the processes that control the shallow seismogenic locking are poorly understood. This study will illuminate regions of locking along the megathrust region by examining the relationship between observed locking, past large earthquakes, current small earthquakes, and variations along the subduction interface. The Northern Costa Rica and Nicaraguan region was chosen because of the wealth of data, recent occurrence of a rare tsunami earthquake, and the unusual proximity of land to the seismogenic interface. The project will be a five-year effort that integrates seismic, geodetic and modeling results, utilizing the diverse geophysical tools for which Newman has expertise. To do this he will improve the regional GPS velocity field with a new campaign in 2010; He will combine existing earthquake datasets, seismic tomography and profiles, along with new events to develop a continuous plate interface model. He will use the seismicity to perform a state-of-the-art analysis of the spatial and temporal variability in the seismicity-rate distribution, and determine its validity as a proxy for locking. If confirmed, the tool will be used to identify such characteristic changes along the seismogenic interface offshore Nicaragua, in the zone of a recent large tsunami earthquake, and where GPS has no resolution.Intellectual Merit: Through analysis of existing and ongoing recordings in Costa Rica, the project will: 1) Develop a new seismicity constrained subduction interface model, for use in further modeling, and interpretation; 2) Explore interseismic changes in earthquake rates throughout the seismogenic zone, for use in understanding regional and time-dependent changes in activity, stress, and observed aseismic slip; 3) Examine the history of large interface earthquakes to determine the regional variability of coupling; and 4) Develop a new regional GPS velocity field for interseismic convergence, and identify any transitory long-period temporal character of convergence. This research will build on in an ongoing 12 station seismic array in Costa Rica that includes four Georgia Tech-owned broad-band seismometers, and will be done in collaboration with an ongoing continuous GPS network in the region. The results will be modeled using the seismically defined interface, and locking results will be compared with seismicity rate mapping to further determine the spatial and temporal variability in the region. If validated as a unique proxy for interface stresses, seismicity-rate (b-value) mapping will be useful for effectively identifying locked zones in offshore regions where geodetic techniques are currently very expensive and less utilized.Broader Impact: This project will improve our understanding of the mechanical controls on shallow subduction seismogenesis and tsunami hazard, having direct societal benefit. Two Georgia Tech graduate students will be supported by this project, where they will be trained to perform research and disseminate results through papers and presentations. The project will support scientific training and infrastructure in Costa Rica. The PI is a beginning investigator, and the project will help develop a dynamic geophysics research group at Georgia Tech. Knowledge gained through the project will be incorporated in courses at Georgia Tech. The program will develop a Georgia educational seismic network that will be used with learning modules to enhance the earth science curriculum in Georgia schools. The schools reached by this program will include a diverse socioeconomic group of students, with the initial target school being a charter school near downtown Atlanta that has primarily low income and minority students.