Hybrid Measurements of Crustal Deformation in Guerrero, Mexico

墨西哥格雷罗州地壳变形的混合测量

• 批准号: 0125618
• 负责人: Kristine Larson
• 金额: $ 29.88万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125618&HistoricalAwards=false
• 关键词: Hybrid; Measurements; Crustal; Deformation; Guerrero

Recent improvements in our understanding of the physics and rheology of fault slip suggest that predictive modeling of fault displacement may be possible in the near future. Such models require observational constraints from both geodesy and seismology, and ideally the observations should encompass time scales greater than that of the earthquake cycle. Working collaboratively with UNAM (National Autonomous University of Mexico), the University of Colorado is developing an integrated model of megathrust fault slip, using data from the state of Guerrero, Mexico. The study area encompasses a ~100 km segment of the Cocos-North America plate boundary with more than 5 m of seismic slip deficit. The geodetic data suggest that significant transient, aseismic slip recently occurred on the Guerrero subduction interface. This poses a fundamental question: does the seismic slip deficit (or "seismic gap") in Guerrero represent a very mature accumulation of plate boundary strain? Or, does the subduction megathrust in Guerrero relieve most of its strain accumulation aseismically? In other words, does transient motion in Guerrero translate to a higher seismic hazard, or a lower hazard, than on other megathrusts? This question is being addressed via a combination of data collection and modeling. The Guerrero gap is being monitored continuously with GPS receivers operated by CU and UNAM. These GPS data are combined to estimate positions on a daily basis and are used as input to the models. The GPS receivers are also being operated at higher rates, 5 Hz, so that higher rate positions can be estimated during earthquakes and combined with seismic data also being collected in Guerrero.

最近我们对断层滑动的物理和流变学的理解的进步表明，在不久的将来，对断层位移进行预测建模是可能的。这种模型需要大地测量学和地震学的观测约束，理想情况下，观测的时间尺度应该大于地震周期的时间尺度。科罗拉多大学与墨西哥国立自治大学(UNAM)合作，利用墨西哥格雷罗州的数据，开发了一个大型逆冲断层滑动的综合模型。研究区包括科科斯-北美板块边界约100公里的一段，地震滑动赤字超过5m。大地测量数据表明，格雷罗俯冲界面最近发生了显著的瞬时无地震滑动。这提出了一个基本问题：格雷罗州的地震滑动赤字(或“地震缺口”)是否代表了板块边界应变的非常成熟的积累？或者，格雷罗州的俯冲巨型断裂带是否在地震上消除了大部分应变积累？换句话说，格雷罗州的瞬时运动是否会导致地震风险比其他巨型逆冲更高，或更低？这一问题正在通过数据收集和建模相结合的方式加以解决。中央大学和联合国大学使用的全球定位系统接收器正在持续监测格雷罗州的缺口。这些GPS数据被组合在一起，以估计每天的位置，并用作模型的输入。GPS接收器也在以更高的频率运行，即5赫兹，这样就可以在地震期间估计更高频率的位置，并与格雷罗州也收集的地震数据结合起来。