Constraining rupture and relaxation dynamics of crustal fault roots with geodetic and microseismic observations

地壳中断裂带的行为随着深度的变化而变化--浅层、脆性区域产生地震，而深部、韧性区域以稳定的方式蠕动。在中等深度(通常是地表以下10至15英里)，“断层根”将脆弱的断层与下方稳定变形的区域连接起来，控制着大地震深入地壳的深度，以及余震的特征和地震后的快速蠕变。这个项目试图通过对余震(来自地震仪)和地表运动(来自GPS)的高分辨率测量，在几秒到几年的时间尺度上，更完整地揭示加州大地震后更深的断裂带的行为。自20世纪90年代初以来，加利福尼亚州南部发生了多达6次6级或更大的地震，S将一起进行研究，以确定它们的断层性质，并确定控制余震数量和规模以及余震持续时间的因素。该项目旨在利用与加州几次大地震(矩震级6级及以上)有关的大地位移和地震活动的同震和震后观测，研究地壳断层孕震带底部的破裂和早期松弛过程。该项目将涉及开发新的观测推断方法，并在这些情况下限制与深度和时间相关的抗震和地震断层行为。对圣安德烈亚斯断裂系统不同事件的不同断裂段的早期震后响应进行对比，将为检验孕震深度余震的控制因素、约束断层摩擦和流变性质、区分早期震后变形机制的转换提供新的机会。该项目的结果将提供整合连续大地测量和地震观测的优秀范例，并潜在地指导基于物理的大地震破裂和地震活动演化模型的发展。该项目由EAR地球物理计划(PH)和既定的激励竞争研究计划(EPSCoR)联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The behavior of fault zones in the Earth’s crust changes with depth - shallow, brittle regions produce earthquakes while deep, ductile regions creep in a stable manner. At intermediate depths (typically 10 to 15 miles below the surface), “fault roots” connect brittle faults to the stably deforming regions below, and control how deep into the crust large earthquakes penetrate, as well as the characteristics of aftershocks and rapid creep following such earthquakes. This project seeks to reveal a more complete picture of deeper fault zone behavior after large California earthquakes , using high-resolution measurements of aftershocks (from seismometers) and surface motions (from GPS), over timescales of seconds to years. Up to six magnitude 6 or greater earthquakes that have occurred in southern California since the early 1990's will be studied together, to characterize their fault properties and identify factors that control the number and size of aftershocks, as well as how long they last. This project aims to use coseismic and postseismic observations of geodetic displacements and seismicity associated with several major earthquakes (moment magnitudes of 6 and above) in California to study the rupture and early relaxation processes at the base of the seismogenic zone of crustal faults. The project will involve developing new methods for observational inferences and constraining the depth- and time-dependent aseismic and seismic fault behavior in these cases. The comparisons of early postseismic responses of different fault segments from different events in the San Andreas fault system will provide new opportunities to test the controlling factors of aftershock generation at seismogenic depths, constrain fault friction and rheological properties, and distinguish the transition of early postseismic deformation mechanisms. The results of this project will provide excellent examples of integrating continuous geodetic and seismic observations, and potentially guide the development of physics-based models of large earthquake ruptures and seismicity evolution.This project is jointly funded by the EAR Geophysics Program (PH) and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.