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.

中文翻译：

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断层岩石性质和条件在南海槽地震破裂传播过程中产生滑移变化


尽管钻探的断层岩石样本已经获得了有关浅层俯冲带摩擦特征的信息，但破裂扩展与摩擦水平和孔隙流体压力的关系仍然不确定。为了研究这个主题，我们沿着 1944 年 Mw 8.0 南海槽 Tonankai 地震期间滑落的 megasplay 断层进行了动态破裂模拟。我们使用了对断层段岩石进行摩擦实验的实际数据，以及从地球物理勘测中推断出的沿断层 0-10 公里深度浅层的预先存在的孔隙压力。低摩擦（摩擦系数约为 0.04）的模拟产生了较大的滑移（约 30 m），而使用较高摩擦（摩擦系数约为 0.2）的模拟则抑制了破裂。在孔隙流体压力几乎等于岩石静应力的低摩擦模拟中，滑移减少到约 25 m。然而，当模拟包括浅层的滑移增强和较高的摩擦力时，滑移仍然达到了大约 20 m。破裂扩展过程中滑移的这种变化是由断层岩的摩擦特性和流体压力条件的差异引起的，其中摩擦特性可能与矿物成分有关。断岩类型的时空非均质性及其物理和水力特性可能从根本上造成地震破裂沿南开板块俯冲边界传播的复杂性和可变性。