Inferring heterogeneity of fault properties and stress state of a megathrust fault from dynamic stress drop variations: A feasibility study in the northern Chilean subduction zone

从动态应力降变化推断断层性质和巨型逆冲断层应力状态的异质性：智利北部俯冲带的可行性研究

• 批准号: 442516884
• 负责人: Dr. Jonas Folesky
• 金额: --
• 依托单位: Department of Earth and Marine Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/442516884?language=en
• 关键词: Inferring; heterogeneity; fault; properties; stress

I propose a research project to systematically investigate the spatiotemporal patterns of seismic stress drop at the seismically highly active northern Chilean subduction zone. For this I plan an integrative analysis approach based on the combination of three independent stress drop estimation techniques.Recent studies indicate that stress drop relates to the fault strength and/or the stress acting on the fault. This suggests that the stress drop may be a valuable parameter to perform fault segmentation to constrain the slipping and locking behavior or to identify potential rupture barriers. However, stress drop estimates often suffer from large uncertainties, comparability between studies is difficult, and the analyzed data sets often are limited. Simultaneously, a well- resolved image of the stress drop distribution in space and time could help greatly to understand the nucleation and rupture processes of megathrust earthquakes.Stress drop measurements are usually derived from corner frequencies of recorded displacement spectra. They involve large uncertainties due to measurement errors and assumptions about earthquake dynamics. To improve the accuracy, I plan to develop a refined methodology which combines three different techniques: a spectral ratio method, a spectral stacking method, and the lower bound approach. The first two approaches are spectra techniques, the third approach is based on the magnitude frequency distribution and earthquake locations. By exploiting the synergies of these techniques, I hypothesize that it will be possible to significantly enhance the robustness and accuracy of the measurements.A particularly interesting study region is the northern Chilean subduction zone which is considered as a seismic gap hosting the potential of a severe megathrust event. In 2014 the region experienced the MW8.1 Iquique megathrust earthquake which only released part of the stored rupture potential. The area has been surveyed by the IPOC network since 2006. Important underlying works such as the compilation of a high resolution seismicity catalog with over 100,000 earthquakes including for- and aftershock series and the detection of long-term repeating earthquake sequences have already been carried out. Additionally, detailed GPS-based studies exist which independently constrain the co-seismic slip and after-slip distribution. Therefore, this data set provides the great possibility analyze thousand of events in a self-consistent manner and to compare the derived stress drop patterns with geodetic results in great detail.The major contribution of the here proposed study will be an advanced method for stress drop estimation. I expect that its application to northern Chile will provide an unprecedentedly detailed image of the stress drop distribution in a subduction zone. Furthermore, it will help to improve our still insufficient knowledge of the relation between stress drop, frictional behavior, and applied stress.

我提出了一个研究项目，系统地研究地震高度活跃的智利北部俯冲带地震应力下降的时空模式。为此，我计划采用一种基于三种独立应力降估计技术相结合的综合分析方法。最近的研究表明，应力降与断层强度和/或作用在断层上的应力有关。这表明应力降可能是执行断层分割以约束滑动和锁定行为或识别潜在破裂屏障的有价值的参数。然而，压力降估计通常存在很大的不确定性，研究之间的可比性很困难，并且分析的数据集通常是有限的。同时，应力降在空间和时间上分布的清晰图像可以极大地帮助理解巨型逆冲地震的成核和破裂过程。应力降测量通常是从记录的位移谱的角频率得出的。由于测量误差和关于地震动力学的假设，它们涉及很大的不确定性。为了提高准确性，我计划开发一种结合三种不同技术的改进方法：光谱比法、光谱叠加法和下限法。前两种方法是频谱技术，第三种方法是基于震级频率分布和地震位置。通过利用这些技术的协同作用，我假设可以显着提高测量的稳健性和准确性。一个特别有趣的研究区域是智利北部俯冲带，该区域被认为是一个可能发生严重逆冲事件的地震间隙。 2014年，该地区经历了MW8.1伊基克逆冲断层地震，仅释放了部分储存的破裂潜力。自2006年起，IPOC网络对该地区进行了调查。包括前震和余震序列在内的超过10万次地震的高分辨率地震活动目录的编制以及长期重复地震序列的检测等重要的基础工作已经开展。此外，还存在基于 GPS 的详细研究，这些研究独立地约束同震滑移和后滑移分布。因此，该数据集提供了以自洽的方式分析数千个事件的巨大可能性，并将导出的应力降模式与大地测量结果进行详细比较。这里提出的研究的主要贡献将是一种先进的应力降估计方法。我预计它在智利北部的应用将提供俯冲带应力降分布的前所未有的详细图像。此外，这将有助于改善我们对应力下降、摩擦行为和施加应力之间关系的认识仍然不足。