Hybrid Measurements of Crustal Deformation in Guerrero, Mexico

最近我们对断层滑动的物理和流变学的理解的改进表明，在不久的将来，断层位移的预测建模可能是可能的。这种模式需要来自大地测量学和地震学的观测约束，理想情况下，观测应该包含比地震周期更大的时间尺度。科罗拉多大学与墨西哥国立自治大学合作，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。研究区包括约100公里的可可斯-北美板块边界段，地震滑差超过5米。大地测量资料表明，最近在格雷罗俯冲界面上发生了明显的瞬态地震滑动。这就提出了一个基本问题：格雷罗的地震滑差（或“地震间隙”）是否代表了一个非常成熟的板块边界应变积累？或者，格雷罗的俯冲巨型逆冲是否在地震上缓解了大部分的应变积累？换句话说，格雷罗的瞬态运动与其他大型逆冲断层相比，是否意味着更高的地震危险性，还是更低的地震危险性？这个问题正在通过数据收集和建模的结合来解决。格雷罗缺口正由CU和UNAM操作的GPS接收器持续监测。这些GPS数据被结合起来，以估计每天的位置，并被用作模型的输入。GPS接收器也在以更高的频率（5hz）运行，因此可以在地震期间估计更高频率的位置，并结合格雷罗收集的地震数据。

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.