Earthquake energy budget and coseismic fault temperature from seismological observations

地震观测中的地震能量收支和同震断层温度

• 批准号: NE/N011791/1
• 负责人: Ana Ferreira
• 金额: $ 48.67万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN011791%2F1
• 关键词: Earthquake; energy; budget; coseismic; fault

How do earthquakes happen? Understanding the nature of earthquakes is a key fundamental question in Geociences that holds many implications for society. Earthquakes are typically associated with a sudden release of energy that has slowly accumulated over hundreds to thousands of years, being strongly controlled by friction in faults buried several kilometers beneath our feet under quite extreme conditions. For example, the amount of heat produced in just a few seconds is such that it can dramatically change the nature of the fault zone near the sliding surface. Moreover, there is abundant evidence of substantial frictional weakening of faults (i.e., fault strength weakens with increasing slip or slip rate) during earthquakes. However, there are still many open questions related to earthquake source processes: How similar are earthquakes in different temperature-pressure conditions? What is the earthquake's energy budget, which controls the intensity of ground motions? What are the physical mechanisms responsible for fault weakening? Recent progress in seismological imaging methods, theoretical fracture mechanics and rupture dynamics simulations can help solve these questions. Huge volumes of freely available seismic and geodetic data from around the world now allow the routine calculation of earthquake models where earthquakes are typically described as single space-time points. Time is now ripe for systematically building robust, more detailed seismic models bearing information on earthquake's physics by using recently developed sophisticated modelling tools along with high-quality images of the 3-D Earth's interior structure enabled by high performance computing facilities. Moreover, it is now possible to model ruptures theoretically in detail using both analytical fracture mechanics calculations and numerical rupture dynamics simulations, and, for example, estimate the fault temperature during the rupture process, which is the most direct way to quantify friction. However, systematic quantitative links between these calculations and seismological observations are still lacking. This project addresses these issues through a coordinated effort involving seismology and rock mechanics aiming at estimating fault temperature rise during earthquakes from new macroscopic seismic source models. We will use advanced seismic source imaging methods to build a new set of robust kinematic, static and dynamic earthquake source parameters for a large selected set of global earthquakes (e.g., average fault length, width, rupture speed and time history, stress drop, radiated and fracture energy). These solutions will then be used as input parameters to estimate fault temperature using analytical and numerical rupture dynamics calculations. This will lead to an improved understanding of how local fault processes occurring at scales from few microns to tens of centimetres translate into macroscopic seismological properties, how energy is partitioned during earthquakes and which are the mechanisms responsible for fault weakening. Ultimately this project will shed new light on many basic questions in earthquake science such as the similarity of earthquakes in different P-T conditions and the potential geological record left by ruptures (e.g., melt). More broadly, this project will benefit hazard models and any studies relying on accurate earthquake source parameters such as studies in seismic tomography, active tectonics and microseismicity (e.g., associated with hydraulic fracturing).

地震是如何发生的？了解地震的性质是地球科学中的一个关键基本问题，对社会有许多影响。地震通常与能量的突然释放有关，这些能量是在数百到数千年的时间里缓慢积累起来的，在相当极端的条件下，这些能量受到埋在我们脚下几公里处的断层的摩擦力的强烈控制。例如，在短短几秒钟内产生的热量可以极大地改变滑动面附近断层带的性质。此外，有大量证据表明断层的摩擦力明显减弱（即，断层强度随着滑动或滑动速率的增加而减弱）。然而，仍然有许多悬而未决的问题与震源过程：如何相似的地震在不同的温度-压力条件？控制地面运动强度的地震能量收支是多少？造成断层弱化的物理机制是什么？地震成像方法、理论断裂力学和破裂动力学模拟的最新进展有助于解决这些问题。世界各地的大量免费地震和大地测量数据现在允许对地震模型进行常规计算，而地震通常被描述为单个时空点。现在时机已经成熟，可以利用最近开发的先进建模工具沿着高性能计算设施所能提供的三维地球内部结构的高质量图像，系统地建立载有地震物理学信息的可靠、更详细的地震模型。此外，现在可以使用分析断裂力学计算和数值断裂动力学模拟在理论上详细建模断裂，例如，估计断裂过程中的断层温度，这是量化摩擦的最直接方法。然而，这些计算和地震观测之间的系统定量联系仍然缺乏。该项目通过涉及地震学和岩石力学的协调努力来解决这些问题，旨在根据新的宏观震源模型估计地震期间断层温升。我们将使用先进的震源成像方法，为一组选定的大型全球地震（例如，平均断层长度、宽度、破裂速度和时间历程、应力降、辐射能和断裂能）。然后，这些解将用作输入参数，通过分析和数值破裂动力学计算来估计断层温度。这将导致更好地了解发生在几微米到几十厘米尺度上的局部断层过程如何转化为宏观地震学特性，地震期间能量如何分配，以及哪些是断层弱化的机制。最终，该项目将为地震科学中的许多基本问题提供新的线索，例如不同P-T条件下地震的相似性以及断裂留下的潜在地质记录（例如，熔化）。更广泛地说，该项目将有利于灾害模型和任何依赖准确震源参数的研究，如地震层析成像、活动构造和微震活动性研究（例如，与水力压裂相关）。

项目成果

The Evolution of Mantle Plumes in East Africa

• DOI: 10.1029/2020jb019929
• 发表时间: 2020-11
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Sung‐Joon Chang;E. Kendall;A. Davaille;A. Ferreira

Comparing global seismic tomography models using varimax principal component analysis

• DOI: 10.5194/se-12-1601-2021
• 发表时间: 2021-07
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: O. de Viron;M. Van Camp;A. Grabkowiak;A. Ferreira

Comparing global seismic tomography models using the varimax Principal Component Analysis

• DOI: 10.5194/se-2021-16
• 发表时间: 2019-12
• 作者: O. de Viron;M. Van Camp;A. Grabkowiak;A. Ferreira

Improving Global Radial Anisotropy Tomography: The Importance of Simultaneously Inverting for Crustal and Mantle Structure

改进全球径向各向异性断层扫描：同时反演地壳和地幔结构的重要性

• DOI: 10.1785/0120160142
• 发表时间: 2017
• 期刊: Bulletin of the Seismological Society of America
• 影响因子: 3
• 作者: Chang S

Extrinsic Elastic Anisotropy in a Compositionally Heterogeneous Earth's Mantle.

成分异质的地幔中的外在弹性各向异性。

• DOI: 10.1029/2018jb016482
• 发表时间: 2019
• 期刊: Journal of geophysical research. Solid earth
• 作者: Faccenda M