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A sequence of main and aftershocks is a complex natural hazard, which may introduce severe damage to critical infrastructure systems. Managing the risk caused by sequential earthquake events is challenging due to the uncertainties of aftershocks and their dependency on the preceding mainshock. Moreover, the dynamic behavior of a structural system under aftershocks must be evaluated with consideration of possible structural damage caused by the mainshock. To overcome these difficulties, this paper proposes a new framework based on a Bayesian network (BN) for risk modelling and inference for structures under a sequence of main and aftershocks. The stochastic mechanisms of sequential earthquakes and the hysteretic behavior of structures are described by BN models, which are then integrated for comprehensive modeling of the risk. The developed BN model facilitates probabilistic inference to obtain fragility curves given various circumstances regarding sequential earthquake events and observations. Numerical examples demonstrate fragility assessment and inference with the proposed BN‐based framework. [ABSTRACT FROM AUTHOR]

Knowledge of what governs the interaction between slow‐ and fast‐slip earthquakes is essential to understanding the nature of the earthquake cycle. In southern Taiwan, four major earthquakes (2008 Mw 5.2 Taoyuan, 2010 Mw 6.4 Jiashian, 2012 Mw 5.9 Wutai, and 2016 Mw 6.4 Meinong events) that occurred near the active tremor areas provide a unique opportunity to analyze their spatiotemporal association. With the declustered tremor catalog built in this study, we were able to statistically evaluate the possible association between tremor and mainshock‐aftershock sequences in space and time. We found that close‐by mainshocks influences tremor's timing in a matter of less than 5 days by short‐term triggering, while the 2010 ML 6.4 Jiashian earthquake appears to be most responsible for such triggering. Assuming a low dip angle thrust faulting mechanism, tremors coincided with small static stress increases (8 kPa) in the 2010 ML 6.4 Jiashian earthquake. The other three major events, however, caused either negative or neglectable stress changes in the tremor zone. The different responses of the tremors can be explained by coseismic slip‐induced static stress change. In this complex tectonic region as a boundary between continental subduction and collision, the interaction between slow‐ and fast‐slip phenomena could be facilitated by a commonly high fluid pressure environment. Key Points: We explore the spatiotemporal association between tremors and earthquakes using 7‐year tremor and earthquake catalogIn a confined distance of 5 km, a greater percentage of earthquakes tend to occur in 5 days prior to the tremorsA commonly high fluid pressure environment may be needed, to facilitate their interaction [ABSTRACT FROM AUTHOR]

Current assumptions on the level of inter-dependency between the magnitudes of earthquakes and the magnitudes of their aftershocks vary significantly, ranging from assumed independence for models like epidemic type aftershock-sequence (ETAS) to assumed positive correlation, at least for the events leading up to the largest earthquakes, for models like accelerated moment release. Recently, a method was developed by Marsan and Lengline for model independent stochastic de-clustering (MISD) of a multidimensional Hawkes self-exciting process, or as is the case here, earthquake activity. After expanding the algorithm to allow for a spatially dependent background rate (henceforth SDMISD), repeated application of SDMISD to a global earthquake catalog allows for estimates with confidence bounds for the average magnitude of an aftershock conditioned upon the magnitude(s) of the earthquake(s) that caused the aftershock. 15 years of data on M 5.3 earthquakes from the global Centroid Moment Tensor earthquake catalog indicate that the magnitudes of aftershocks are dependent on the magnitudes of the earthquakes that cause them, and indeed, larger than average earthquakes are more likely to trigger larger than average aftershocks. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]