Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with \(M_L=3.6\) was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity.

中文翻译：

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荷兰格罗宁根气田基于应力的诱发地震活动统计模型

格罗宁根是欧洲正在生产的最大的陆上天然气田。气田的压力衰竭始于1963年。1991年，在随后的几十年中，随着储层水平的上升，首次诱发了微地震。这些事件大多数都小于2.0，无法感知。但是，多年来，最大观测到的震级不断增加，直到发生最大的重大事件（\ M_L = 3.6 \）记录在2014年，最终导致决定减产。该因果序列显示出对生产和诱发地震活动之间的关系进行理解和建模以及对经济计划和危害评估的关键作用。在这里，我们测试与天然气勘探有关的诱发地震活动是否可以通过具有速率和状态相关的摩擦行为的断层网络的统计响应来建模。我们使用冗长而完整的本地地震目录，并使用有关储层水平因生产而引起的变化的详细信息来测试不同的地震活动模型。流体压力和储层压实度的变化都作为输入来测试，以近似库仑应力变化。我们发现具有恒定构造背景地震活动率的速率和状态模型可以重现观察到的地震活动开始的长时间延迟。相反，具有瞬时地震成核作用的所谓库仑破坏模型需要假设所有断层最初都远离应力的临界状态才能解释这种延迟。我们基于流体孔隙压力的速率和状态模型最适合地震活动的时空模式，其中通过考虑断层密度和方向进一步提高了拟合度。尽管速率和状态模型仅具有三个自由参数，但它很简单，它可以重现观察到的活动的主要统计特征。具有瞬时地震成核作用的所谓库仑破坏模型需要假设所有断层最初都远离临界应力状态才能解释这种延迟。我们基于流体孔隙压力的速率和状态模型最适合地震活动的时空模式，其中通过考虑断层密度和方向进一步提高了拟合度。尽管速率和状态模型仅具有三个自由参数，但它很简单，它可以重现观察到的活动的主要统计特征。具有瞬时地震成核作用的所谓库仑破坏模型需要假设所有断层最初都远离应力的临界状态，才能解释这种延迟。我们基于流体孔隙压力的速率和状态模型最适合地震活动的时空模式，其中通过考虑断层密度和方向进一步提高了拟合度。尽管速率和状态模型仅具有三个自由参数，但它很简单，它可以重现观察到的活动的主要统计特征。