Fault rock properties and conditions produce variance in slip during earthquake rupture propagation at the Nankai Trough

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Tectonophysics Pub Date : 2024-08-22 DOI:10.1016/j.tecto.2024.230483
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Abstract

Although drilled samples of fault rocks have yielded information on frictional features of shallow subduction zones, the relationship of rupture propagation to the levels of friction and pore-fluid pressure remains uncertain. To investigate this topic, we performed dynamic rupture simulations along the megasplay fault that slipped during the 1944 Mw 8.0 Tonankai earthquake in the Nankai Trough. We used actual data from friction experiments on rocks from the fault segment and pre-existing pore pressures deduced from geophysical surveys for the shallow portion of 0–10 km depth along the fault. Simulations of low friction (friction coefficient ca. 0.04) produced large slip (about 30 m), whereas simulations using higher friction (friction coefficient ca. 0.2) suppressed the rupture. In simulations with low friction in which the pore-fluid pressure was nearly equal to the lithostatic stress, the slip decreased to about 25 m. However, when the simulations included slip-strengthening at shallow depth and higher friction, the slip still reached roughly 20 m. Such variability in slip during rupture propagation is caused by differences in the friction features and fluid pressure conditions of fault rocks, in which the friction features might be related to the mineral composition. Spatiotemporal heterogeneity in fault-rock type and their physical and hydraulic properties may fundamentally produce the complexity and variability of earthquake rupture propagation along the Nankai plate-subduction boundary.

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断层岩特性和条件在南海海槽地震破裂传播过程中产生的滑移差异
尽管对断层岩石的钻探样本已经提供了浅俯冲带摩擦特征的信息,但断裂传播与摩擦力和孔隙流体压力水平的关系仍不确定。为了研究这个问题,我们沿着 1944 年南海海槽发生 8.0 级砺石海地震时滑动的巨型断层进行了动态断裂模拟。我们使用了断层段岩石摩擦实验的实际数据,以及地球物理勘测推断出的断层沿线 0-10 千米深度浅层部分的原有孔隙压力。低摩擦力(摩擦系数约为 0.04)模拟产生了大滑移(约 30 米),而高摩擦力(摩擦系数约为 0.2)模拟则抑制了断裂。在孔隙流体压力几乎等于岩石应力的低摩擦力模拟中,滑移量减少到约 25 米。然而,当模拟包括浅层滑移加强和较高摩擦力时,滑移量仍达到约 20 米。断层传播过程中滑移量的这种变化是由断层岩石的摩擦特征和流体压力条件的差异造成的,其中摩擦特征可能与矿物成分有关。断层岩类型及其物理和水力特性的时空异质性可能从根本上导致南海板块-俯冲边界地震破裂传播的复杂性和多变性。
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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