Active fault slip-rates and earthquake recurrence controlled by stress transfer and viscous flow

断层上无法解释的滑动率波动阻碍了地震危险性评估和对大陆变形的理解，这些波动与（a）持续100到1000年的破坏性地震的时间集群和（B）持续数十到数十万年的长期断层平静有关。我们提出了一个新的统一假设来解释（a）和（B），涉及断层/剪切带和相邻断层/剪切带之间的应力相互作用;然而，缺乏关键数据来测试这一点。我们提出了测量和建模来测试我们的假设，这有可能量化控制大陆断层和预期地震发生率波动的过程，具有很高的社会影响。我们的愿望是，通过使用我们在此开创的计算，世界各地的城市和关键设施将获得额外的保护，免受地震危害。其背景是，滑动率波动阻碍了理解，因为它们引入了关于特定断层是否活跃的不确定性。例如，日本对敦贺核电站（NPP）等关键设施的地震风险进行了审查，发现核反应堆下方存在地质断层（Chapman等人，2014年）。所产生的问题是断层是否活动。日本核管理局（NRA）有定义断层活动的指导方针，并认为反应堆下的断层是活跃的，证据是年龄<125，000年的沉积物中的断层。日本原子能电力公司（JPAC）在一个独立的地球科学家小组进行研究后表示不同意。2014年，敦贺核电站由于NRA和JPAC之间的持续辩论而仍然关闭，其他核电站也在进行类似的辩论。我们认为，定义为简单的“活跃”或“不活跃”的故障活动是不能令人满意的，因为它是有争议的，甚至在专家。事实上，一个几千年来没有滑动的断层实际上可能不是不活动的，而是可能只是滑动率很低，在很长的重复间隔之后，有能力承载破坏性的地震。我们的突破是，我们认为在两个时间尺度（a和B）的滑动率波动是一个连续体，共享一个共同的原因，涉及断层/剪切带之间的相互作用。这是第一次，我们提供了计算，描述这种相互作用，量化滑动率波动和地震危险的概率。我们表明，在地震群中的滑动脆性断层在上地壳发生在串联与高应变率的粘性剪切带的故障。地壳的这种变形在邻近的断层/剪切带上产生差应力的变化。已知粘性应变率与差应力成比例，因此，给定滑动率波动的数据，可以计算差应力的变化，然后计算接收剪切带上粘性应变率的隐含变化以及其上覆脆性断层上的滑动率。我们提供了一个涵盖数千年的量化例子，但缺乏允许测试数十万至数十万年的数据。如果我们能够在两个时间尺度上验证我们的假设，通过建模成功地复制测量结果，我们将确定和量化一个迄今未知的基本地质过程。我们将研究雅典地区，希腊，一组特殊的地质属性，使我们能够测量和模型的滑动率波动在两个时间尺度（a和B），关键的数据组合从来没有实现的日期。我们知道没有其他量化的解释可以将两个时间尺度上的滑动率波动联系起来;实现这一点的意义和影响在于，它有可能改变我们减轻城市和关键设施危害的方式。Chapman等人。2014，活动断层和核电厂，EOS，95，4

Seismic hazard assessment and understanding of continental deformation are hindered by unexplained slip-rate fluctuations on faults, associated with (a) temporal clusters of damaging earthquakes lasting 100s to 1000s of years, and (b) longer-term fault quiescence lasting tens to hundreds of millennia. We propose a new unified hypothesis explaining both (a) and (b), involving stress interactions between fault/shear-zones and neighbouring fault/shear-zones; however key data to test this are lacking. We propose measurements and modelling to test our hypothesis, which have the potential to quantify the processes that control continental faulting and fluctuations in the rates of expected earthquake occurrence, with high societal impact. Our aspiration is that cities and critical facilities worldwide will gain additional protection from seismic hazard through use of the calculations we pioneer herein. The background is that slip-rate fluctuations hinder understanding because they introduce uncertainty about whether specific faults are active or not. For example, a review in Japan of earthquake risk to critical facilities, such as the Tsuruga nuclear power plant (NPP), revealed a geological fault under a nuclear reactor (Chapman et al. 2014). The question that arose was whether the fault was active or not. Japan's Nuclear Regulatory Authority (NRA) has guidelines defining fault activity, and considered the fault under the reactor to be active, evidenced by faulting in sediments <~125,000 years in age. The Japan Atomic Energy Power Company (JPAC) disagreed, following study by an independent team of geoscientists. In 2014, the Tsuruga NPP remained closed due to ongoing debate between the NRA and JPAC, with similar debates ongoing for other NPPs. We suggest that defining fault activity as simply "active" or "inactive" is unsatisfactory because it is debatable even amongst experts. In fact a fault that has not slipped in many millennia may, in reality, not be inactive, but instead may simply have a low slip-rate, with the capability to host a damaging earthquake after a long recurrence interval. Our breakthrough is we think slip-rate fluctuations over both timescales (a and b) are a continuum, sharing a common cause involving interaction between fault/shear-zones. For the first time, we provide calculations that describe this interaction, quantifying slip-rate fluctuations and seismic hazard in terms of probabilities. We show that slip during an earthquake cluster on a brittle fault in the upper crust occurs in tandem with high strain-rate on the viscous shear-zone underlying the fault. This deformation of the crust produces changes in differential stress on neighbouring fault/shear-zones. Viscous strain-rate is known to be proportional to differential stress, so, given data on slip-rate fluctuations one can calculate changes in differential stress, and then calculate implied changes to viscous strain-rates on receiver shear zones and slip-rates on their overlying brittle faults. We provide a quantified example covering several millennia, but lack data allowing a test over tens to hundreds of millennia. If we can verify our hypothesis over both timescales, through successful replication of measurements via modelling, we will have identified and quantified a hitherto unknown fundamental geological process. We will study the Athens region, Greece, where a special set of geological attributes allows us to measure and model slip-rate fluctuation over both time scales (a and b), the key data combination never achieved to date. We know of no other quantified explanation that links slip-rate fluctuations over the two timescales; the significance and impact of accomplishing this is that it has the potential to change the way we mitigate hazard for cities and critical facilities.Chapman et al. 2014, Active faults and nuclear power plants, EOS, 95, 4