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Given the probability distribution function relating to the recurrence interval and the occurrence time of the previous occurrence of a fault, a time-dependent model of a particular fault for seismic hazard assessment was developed that takes into account the active fault rupture cyclic characteristics during a particular lifetime up to the present time. The Gutenberg and Richter (1944) exponential frequency-magnitude relation uses to describe the earthquake recurrence rate for a regional source. It is a reference for developing a composite procedure modelled the occurrence rate for the large earthquake of a fault when the activity information is shortage. The time-dependent model was used to describe the fault characteristic behavior. The seismic hazards contribution from all sources, including both time-dependent and time-independent models, were then added together to obtain the annual total lifetime hazard curves. The effects of time-dependent and time-independent models of fault [e.g., Brownian passage time (BPT) and Poisson, respectively] in hazard calculations are also discussed. The proposed fault model result shows that the seismic demands of near fault areas are lower than the current hazard estimation where the time-dependent model was used on those faults, particularly, the elapsed time since the last event of the faults (such as the Chelungpu fault) are short. [ABSTRACT FROM AUTHOR]

Engineering risk assessment is to estimate the structure's failure probability multiplied by its failure consequences. On the other hand, the analysis was sometimes performed on a more general basis, utilizing a few indicators to quantify relative risk levels for decision-making. On the basis of such a framework, this paper introduces a novel risk assessment on 18 active faults in Taiwan, considering the fault's location, earthquake size and return period from the literature. The result shows that the Chelungpu Fault in central Taiwan has the highest risk score among the 18 active faults, in contrast to the Hengchun Fault in southern Taiwan which has the lowest risk. Besides this, the 18 active faults in Taiwan were classified into four groups based on this risk assessment, and the classification could help the region's sustainable development against earthquake hazard. [ABSTRACT FROM AUTHOR]

According to the Central Geological Survey Taiwan (CGST), the Meishan fault in Central Taiwan, which induced a catastrophic earthquake in 1906, is considered capable of triggering equivalent events with a return period of 162 years. Therefore, as the next event is expected around 2070, the Meishan fault poses a high level of earthquake risk in Central Taiwan, especially for those cities and townships very close to the fault. However, the best-estimate return period (162 years) and earthquake magnitude (7.1 M) reported by the CGST must be subject to some uncertainty, because such an event is very unlikely to recur every 162 years. Therefore, this study carried out a series of seismic hazard assessments for three major cities close to the Meishan fault, with the uncertainty of the best-estimate information being determined using the Rosenblueth algorithm. The results show that for Chaiyi city, which the Meishan fault passes through, the probability of the current design value (i.e., PGA = 0.33 g) being exceeded by the earthquake motion induced by the Meishan fault in the next 50 years would be as high as 55 %. Therefore, further studies should be carried out to obtain a better understanding of the Meishan fault, to develop a robust hazard mitigation plan for nearby cities. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the results of a case study of the annual probability and return period of soil liquefaction in Yuanlin, Taiwan, the town that suffered significant liquefaction damage in the 1999 Chi-Chi earthquake, are presented. As part of this case study, a framework for determining the average annual probability of liquefaction (AAPL) that is attributed to a known fault is developed. This framework is formulated by considering the uncertainties in both liquefaction resistance and liquefaction loading. For liquefaction loading, the seismic hazard from a known fault is considered; and for liquefaction resistance, soil parameters, characterized mainly by cone penetration test (CPT) and standard penetration test (SPT), and their uncertainties are considered. Additionally, model uncertainty of the empirically-developed liquefaction resistance models, based either on CPT or SPT, is considered in the analysis for the annual liquefaction probabilities. The results of the case study show that the proposed framework is applicable for site-specific analysis of liquefaction potential or for mapping liquefaction potential in a given town (or city). Furthermore, the AAPL and return period determined based on SPTs are found to be comparable with those determined with CPTs. The results of the case study provide some guidance for future engineering planning and regulation consideration in the Yuanlin, Taiwan area. [Copyright &y& Elsevier]

The Shanchiao fault, located to the west of the Taipei Basin in northern Taiwan, is a highly active normal fault that has a left-slip component and fault length of over 40 km. We suggest that the Shanchiao fault still has the ability to induce coseismic subsidence in the Taipei Basin under present extensional regime of northern Taiwan. In order to characterize the coseismic ground deformation and assess the potential inundation hazards in Taipei Basin, we estimate surface displacements using elastic dislocation models. The largest slip is assumed to be located underneath the Kuandu area due to the observation of deepest Tertiary basement in this area. Based on the topography changes due to coseismic deformation in a potential magnitude 7 event induced by reactivation of the Shanchiao fault, a 2D inundation model was adopted to simulate several inundation scenarios, including potential flood inundation below high tide condition and under various return-period design rainfall events. The predicted inundation maps based on various return-period flood events can provide information to assess potential earthquake-induced inundation hazards. [ABSTRACT FROM AUTHOR]

We use seismic and geodetic measurements to optimize the fault geometry as well as coseismic slip distribution from the 2018 Mw 6.4 Hualien earthquake. We find that at least three faults were involved in the earthquake. The earthquake initiated from a south‐dipping fault in offshore Hualien, and slip transferred into the main west‐dipping oblique fault. The slip finally triggered movement of the east‐dipping Milun fault at shallower depth and caused surface rupture. Although there is no offshore data constraints, our inverted slip distribution shows that the majority of slip occurred between 5‐ and 10‐km depth on the main west‐dipping fault, and 1‐ to 3‐m slip on the shallower part of the Milun fault. Additionally, we process 5 months of postseismic deformation time series and find more than 5‐cm postseismic displacement occurred along the Milun fault but is insignificant near the Coastal Range located south of the Hualien City. Plain Language Summary: Taiwan is one of the most tectonically active regions in the world. In eastern Taiwan, the Longitudinal Valley is located between the Eurasian Plate and the Philippine Sea Plate, and the rapid plate collision has cause high surface deformation as well as earthquake hazard in Hualien, the biggest city in northern Longitudinal Valley. In this study, we use measurements during the earthquake to study the fault geometry and fault slip due to the Mw 6.4 Hualien earthquake occurred in February 2018. Our inversion results show that at least three faults are involved in the event, including a south‐dipping fault, a main west‐dipping fault, and the east‐dipping Milun fault located in the Hualien City. Our inverted fault slip at shallower depth is in agreement with field investigation after the earthquake. We also process 5 months of data to observe postearthquake surface deformation and find that there is more than 5 cm of displacement along the Milun fault, but insignificant displacement south of the Hualien City. Key Points: At least three faults were involved in the 2018 Mw 6.4 Hualien earthquakeMost of the slip occurred on the main west‐dipping fault close to the north Coastal RangeRapid postseismic transient along the Milun fault in the Hualien City, whereas insignificant displacement close to the Coastal Range [ABSTRACT FROM AUTHOR]