Major Earthquakes around Taipei and a Seismic Hazard Assessment with Monte Carlo Simulation (original) (raw)
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Seismic Hazard Assessment for the Tianshui Urban Area, Gansu Province, China
International Journal of Geophysics, 2012
A scenario seismic hazard analysis was performed for the city of Tianshui. The scenario hazard analysis utilized the best available geologic and seismological information as well as composite source model (i.e., ground motion simulation) to derive ground motion hazards in terms of acceleration time histories, peak values (e.g., peak ground acceleration and peak ground velocity), and response spectra. This study confirms that Tianshui is facing significant seismic hazard, and certain mitigation measures, such as better seismic design for buildings and other structures, should be developed and implemented. This study shows that PGA of 0.3 g (equivalent to Chinese intensity VIII) should be considered for seismic design of general building and PGA of 0.4 g (equivalent to Chinese intensity IX) for seismic design of critical facility in Tianshui.
Natural Hazards, 2000
The paper describes an integrated approach to seismic hazard assessment, which was applied to the Taiwan region. First, empirical models for ground motion estimation in the region were obtained on the basis of records from recent (1993)(1994)(1995)(1996)(1997)(1998)(1999) earthquakes. The database includes strong-motion data collected during the recent Chi-Chi earthquake (M = 7.6, 21 September 1999) and large (M = 6.8) aftershocks. The ground-motion database was also used for evaluation of generalised site amplification functions for typical soil classes (B, C and D). Second, the theoretical seismic catalogue (2001-2050) for the Taiwan region had been calculated using the 4D-model (location, depth, time) for dynamic deformation of the Earth' crust and 5D-model (location, depth, time, magnitude) for seismic process. The models were developed on the basis of available geophysical and geodynamic data that include regional seismic catalogue. Third, the region and site and timedependent seismic analysis, which is based on schemes of probable earthquake zones evaluated from the theoretical catalogue, regional ground motion models, and local site response characteristics, has been performed. The seismic hazard maps are compiled in terms of Peak Ground Acceleration (PGA) and Response Spectra (RS) amplitudes. The maps show distribution of amplitudes that will not be exceeded with certain probability in condition of typical soil classes during all possible earthquakes that may occur in the region during time period of 2003-2025. The approach allows introduction of a new parameter that describes the dependency of seismic hazard on time, the so-called "period of maximum hazard". The parameter shows the period, during which every considered site will be subjected by the maximum value of ground motion characteristic (PGA or RS).
Deterministic seismic hazard parameters and engineering risk implications for the Hong Kong region
Journal of Asian Earth Sciences, 2001
The paper reviews and compares recent regional studies evaluating the seismic hazard parameters required to assess the seismic risk to engineering construction in the Coastal Region of South China (CRSC) including Hong Kong (HK). The review establishes that the CRSC, and in particular the offshore seismic belt, has mean earthquake magnitude recurrence intervals (MRIs) or return periods that are 2±3 times shorter than those in the eastern United States (EUS), with which the HK region has been compared. An ensemble of realistic design-level earthquake events suitable for de®ning the regional seismic hazard and for undertaking engineering risk assessment is then formulated, in the form of deterministic magnitude±distance pairs associated with earthquake magnitudes having a range of MRIs, and the signi®cance of the maximum credible earthquake (MCE) magnitude is highlighted. Next, the scenario earthquake events have been used to predict the expected levels of peak design ground motions (for bedrock) in the HK region. The approximate method proposed here indicates that peak (effective) ground accelerations may reasonably be estimated to be around 10% g for 500-year earthquake events and 15±20% g for 1000-year events. However, the predicted ground motions arising from design-level earthquake events indicate large uncertainties arising from the attenuation equations. The uncertainties arise from both epistemic (event-to-event) and aleatory (site-to-site) considerations. These uncertainties represent the greatest source of errors in de®ning the seismic hazard for engineering design purposes. Further research is required to de®ne the attenuation characteristics of ground motions for the CRSC, across a range of parameters including ground displacement and velocity as well as acceleration. It is further found that the Chinese earthquake building code gives a reasonably conservative estimate of seismic demand for the region, and is quite consistent with results from both probabilistic and pseudo-probabilistic seismic hazard analysis carried out herein, and by other researchers over the past 7 years. Finally, a discussion is presented of some key issues related to earthquake-resistant design and performance in Hong Kong, including the necessity to consider a range of design-level events with different MRIs when implementing acceptable structural design for earthquake effects. q
Seismic Hazard and Risk Assessments for Beijing–Tianjin–Tangshan, China, Area
Pure and Applied Geophysics, 2011
Seismic hazard and risk in the Beijing-Tianjin-Tangshan, China, area were estimated from 500-year intensity observations. First, we digitized the intensity observations (maps) using ArcGIS with a cell size of 0.1 9 0.1°. Second, we performed a statistical analysis on the digitized intensity data, determined an average b value (0.39), and derived the intensity-frequency relationship (hazard curve) for each cell. Finally, based on a Poisson model for earthquake occurrence, we calculated seismic risk in terms of a probability of I C 7, 8, or 9 in 50 years. We also calculated the corresponding 10 percent probability of exceedance of these intensities in 50 years. The advantages of assessing seismic hazard and risk from intensity records are that (1) fewer assumptions (i.e., earthquake source and ground motion attenuation) are made, and (2) site-effect is included. Our study shows that the area has high seismic hazard and risk. Our study also suggests that current design peak ground acceleration or intensity for the area may not be adequate.
Bulletin of the Seismological Society of America, 2012
In this study, we use extreme value theory based on Gumbel-equation derivations to estimate the Gutenberg-Richter a and b parameters for Taiwan. Data are from the augmented, homogenized (in terms of moment magnitude), historic catalog for Taiwan. The island is divided into grids of 0.2°latitude by 0.2°longitude, and Gumbel type 1 statistical analysis is applied. The values of a and b are then used to determine the probability of large earthquakes (M w ≥ 6:0) occurring at each grid. The results show two relatively high probability paths for large earthquakes, one extending from Hsinchu southward to Taichung, Chiayi, and Tainan in western Taiwan and the other from Ilan southward to Hualian and Taitung in eastern Taiwan, both of which are characterized by low b-values. It indicates that future earthquakes can be expected along these paths characterized by low b-values. Additionally, maximum peak ground acceleration and maximum peak ground velocity (determined from respective attenuation laws and a gridding regimen of 0.1°latitude by 0.1°longitude for Taiwan) follow similar paths to that of the low b-values.
Seismic risk assessment of a large metropolitan area by means of simulated earthquakes
The determination of seismic risk in urban settlements has received increasing attention in the scientific community during the last decades since it allows to identify the most vulnerable portions of urban areas and therefore to plan opportune strategies for seismic risk reduction. In order to accurately evaluate the seismic risk of urban settlements it should be necessary to estimate in detail the seismic vulnerability of all the existing buildings in the considered area. This task could be very cumbersome due to both the great number of information needed to accurately characterize each building and the huge related computational effort. Several simplified methods for the assessment of the seismic vulnerability of existing buildings have been therefore presented in the literature. In order to estimate the occurrence of damage in buildings due to possible seismic excitations, the published studies usually refer to response spectra evaluated according to seismic events expected in ...
Early Estimation of Seismic Hazard for Strong Earthquakes in Taiwan
Natural Hazards, 2006
A shakemap system providing rapid estimates of strong ground shaking could be useful for emergency response providers in a damaging earthquake. A hybrid procedure, which combines site-dependent ground motion prediction models and the limited observations of the Real-Time Digital stream output system (RTD system operated by Central Weather Bureau, CWB), was set up to provide a high-resolution shakemap in a near-real-time manner after damaging earthquakes in Taiwan. One of the main factors that affect the result of ground motion prediction analysis is the existence of site effects. The purpose of this paper is to investigate the local site effects and their influence in the ground shaking and then establish an early estimation procedure of potential hazard for damaging earthquakes. Based on the attenuation law, the site effects of each TSMIP station are discussed in terms of a bias function that is site and intensity-level dependent function. The standard deviation of the site-dependent ground motion prediction model can be significantly reduced. The nonlinear behavior of ground soil is automatically taken into account in the intensity-level dependent bias function. Both the PGA and the spectral acceleration are studied in this study. Based on the RTD data, event correctors are calculated and applied to precisely estimate the shakemap of damaging earthquakes for emergency response.
Empirical Study of the Frequency and Severity of Earthquakes in Taiwan
The rate at which earthquake occurs in Taiwan was investigated for the period of fifty years (1961 – 2010). The result shows that the study area is characterized predominantly by minor, light and moderate earthquakes with the percentage of strong and major extremely low. The result also revealed that for each magnitude range, the number of shallow focus earthquakes is more than the intermediate focus earthquakes. No deep focus earthquake was observed. The shallow earthquake events with magnitude 4.0-4.9 (light) were the most frequent, followed by 5.0-5.9 (moderate), 3.0-3.9 (minor), 6.0-6.9 (strong) and the least frequent were with magnitude 7.0-7.9 (major). While for intermediate earthquakes, events with magnitude 4.0-4.9 were the most frequent, followed by 3.0-3.9, 5.0-5.9, 6.0-6.9 and the least frequent with magnitude 7.0-7.9. It was also discovered that about three (3) shallow earthquakes occur monthly and about two (2) intermediate earthquakes occur yearly in Taiwan on the average. Furthermore the b-values were calculated for shallow and intermediate focus earthquakes to be 0.80 and 0.74 respectively. The b-values were calculated using the Gutenberg-Richter Relation. The low b-value indicates localized high stresses which are favourable for future rupture.
2008
The great Sanhe-Pinggu earthquake (M~8, with the maximum intensity of XI at the epicenter and VIII in Beijing city) occurred in September, 1679 is the largest historic event in the past 500 years within a 100-km radius from the center of Beijing. A detailed comprehension of the ground motion scenario caused by this earthquake will provide valuable information for seismic hazard reduction in the metropolitan Beijing area. Numerical simulation of seismic wave propagation and strong ground motion using high performance computational methods is a proven tool in seismic hazard zonation and local site effect assessment based on scenario earthquakes. We studied the effect of the 1679 Sanhe-Pinggu M8 earthquake in Beijing area with the staggered grid pseudospectral time domain (PSTD) method, with stretched coordinate perfectly matched layer (PML) absorption boundary conditions. The epicenter of this great event was about 60 km ENE of the center of Beijing city. The simulated seismic source ...