Integrating faults and past earthquakes into a probabilistic seismic hazard model for peninsular Italy
Integrating faults and past earthquakes into a probabilistic seismic hazard model for peninsular Italy
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将断层和过去的地震整合到意大利半岛的概率地震灾害模型中
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
B. Pace
中科院分区：
文献类型：
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作者：
A. Valentini;F. Visini;B. Pace
意大利是欧洲地震最活跃的国家之一。历史上，许多活动断层都发生过震级高达 7级的中强震。目前，意大利的概率地震危险性评估主要基于区域震源模型，其中地震活动性是使用一些地震构造带来模拟的，并且假定地震的发生是均匀的。然而，在过去的十年中，人们越来越多地致力于在地震危险模型中使用断层源，以获得更详细和可能更真实的地面运动模式。在我们的模型中，我们使用了两类震源。第一种方法涉及活动断层，并使用地质滑动率来量化地震活动率。我们制作了一份所有断层源的清单，详细说明了它们的几何、运动学和能量特性。利用相关参数计算各断层的总地震矩率。我们使用两个模型来评估每个断层源的震级-频率分布（MFD）：一个以最大震级为中心的特征高斯模型和一个截断的Gutenberg-Richter模型。第二类震源涉及格点地震活动性，采用固定半径平滑方法和历史目录来评估地震活动性。在形变集中于断层方向的假设下，将由活动断层几何形态和滑动速率得到的地震动态面与空间平滑震源得到的地震动态面结合起来，假设活动断层附近的平滑地震活动受断层尺寸驱动因子的影响逐渐减弱。此外，我们计算了475年和2475年的水平峰值地面加速度（PGA）图。虽然这里得到的预期加速度的范围和总空间分布与通过地震目录和经典分区模型得到的结果相当，但我们的模型得到的危险图的空间格局要详细得多。我们的模型的特点是更危险的区域，对应于绘制的活动断层，而以前的模型产生的预期加速度几乎均匀分布在大区域。此外，我们还进行了敏感性测试，以确定两种断层MFD模型得出的地震率对危害结果的影响，并确定断层对分布地震活动的相对贡献。我们相信，我们的模型在输入数据（数量和质量）和意大利基于断层的区域地震危险建模领域使用的方法方面取得了进步。
Italy is one of the most seismically active countries in Europe. Moderate to strong earthquakes, with magnitudes of up to ∼ 7, have been historically recorded for many active faults. Currently, probabilistic seismic hazard assessments in Italy are mainly based on area source models, in which seismicity is modelled using a number of seismotectonic zones and the occurrence of earthquakes is assumed uniform. However, in the past decade, efforts have increasingly been directed towards using fault sources in seismic hazard models to obtain more detailed and potentially more realistic patterns of ground motion. In our model, we used two categories of earthquake sources. The first involves active faults, and using geological slip rates to quantify the seismic activity rate. We produced an inventory of all fault sources with details of their geometric, kinematic, and energetic properties. The associated parameters were used to compute the total seismic moment rate of each fault. We evaluated the magnitude–frequency distribution (MFD) of each fault source using two models: a characteristic Gaussian model centred at the maximum magnitude and a truncated Gutenberg–Richter model. The second earthquake source category involves grid-point seismicity, with a fixed-radius smoothed approach and a historical catalogue were used to evaluate seismic activity. Under the assumption that deformation is concentrated along faults, we combined the MFD derived from the geometry and slip rates of active faults with the MFD from the spatially smoothed earthquake sources and assumed that the smoothed seismic activity in the vicinity of an active fault gradually decreases by a fault-size-driven factor. Additionally, we computed horizontal peak ground acceleration (PGA) maps for return periods of 475 and 2475 years. Although the ranges and gross spatial distributions of the expected accelerations obtained here are comparable to those obtained through methods involving seismic catalogues and classical zonation models, the spatial pattern of the hazard maps obtained with our model is far more detailed. Our model is characterized by areas that are more hazardous and that correspond to mapped active faults, while previous models yield expected accelerations that are almost uniformly distributed across large regions. In addition, we conducted sensitivity tests to determine the impact on the hazard results of the earthquake rates derived from two MFD models for faults and to determine the relative contributions of faults versus distributed seismic activity. We believe that our model represents advancements in terms of the input data (quantity and quality) and methodology used in the field of fault-based regional seismic hazard modelling in Italy.