Evolution of Coulomb failure stress in Sulaiman Lobe,Pakistan,and its implications for seismic hazard assessment

In this research work,we present the evolution of Coulomb failure stress(CFS)in the Sulaiman Lobe and its implications for seismic hazard assessment.The Chaman transform fault,~1,000 km long,is the major active fault that marks the western boundary between Pakistan and Afghanistan on the Indian Plate.To date,few studies have been conducted to unveil the interactions among earthquakes and the implications of these interactions for seismic hazard assessment in the region.We thoroughly investigated the published and online catalog to construct a sequence of major earthquakes that occurred in this region during the past.The final earthquake sequence was composed of 15 earthquakes of M_(w)≥6.0,beginning with the 1888 earthquake.We used the stress-triggering theory to numerically simulate the evolution of CFS caused by these earthquakes.The numerical results revealed that 8 out of 15earthquakes were triggered by the preceding earthquakes.The earthquakes in 1908,1910,1935,1966,and 1997 were rather independent earthquakes in this sequence.Although the epicenters of the 1975a and 1975b earthquakes were in the stress shadow zone,the partial rupture segments of both these earthquakes were in high-CFS regions.The CFS induced by the 1935 earthquake was notable,as it later triggered the 2008 doublet.Moreover,our results revealed that the northern segment of the Chaman Fault,the southern segment of the Ghazaband Fault,and the northwestern segment of the Urghargai Fault demonstrated a high change in CFS that could trigger seismicity in these regions.The necessary arrangements must therefore be made to mitigate any possible seismic hazards in the region.

Seismic Hazard Assessment for Japan after the 2011 Tohoku-Oki Mega-Thrust Earthquake （Mw9.0）

The Tohoku-Oki earthquake （Mw 9.0） of March 11,2011, was the largest event in the history of Japan. This magnitude 9.0 mega-thrust earthquake initiated approximately 100 km off-shore of Miyagi prefecture and the rupture extended 400-500 km along the Pacific plate. Due to the strong ground motions and tsunami associated by this event, approximately twenty thousand people were killed or missing and more than 220 thousands houses and buildings were totally or partially destroyed. This mega-thrust earthquake was not considered in the national seismic hazard maps for Japan that was published by the HERP （headquarters for earthquake research promotion） of Japan. By comparing the results of the seismic hazard assessment and observed strong ground motions, we understand that the results of assessment were underestimated in Fukushima prefecture and northern part of Ibaraki prefecture. Its cause primarily lies in that it failed to evaluate the Mw 9.0 mega-thrust earthquake in the long-term evaluation for seismic activities. On the other hand, another cause is that we could not make the functional framework which is prepared for treatment of uncertainty for probabilistic seismic hazard assessment work fully. Based on the lessons learned from this earthquake disaster and the experience that we have engaged in the seismic hazard mapping project of Japan, we consider problems and issues to be resolved for probabilistic seismic hazard assessment and make new proposals to improve probabilistic seismic hazard assessment for Japan.

Seismic Hazard Matrix of Buildings in Yunnan

Seismologists have begun to investigate the earthquake damage and assess the economic losses on the spot in the Yunnan area since the earthquakes with M_S6.7 and M_S6.9 that occurred on the boundary between China and Myanmar west of Menglian county,Yunnan Province,on April 23,1992.From 1992 to 2003,50 destructive earthquakes occurred in Yunnan,and large amounts of data on seismic hazard have been accumulated.With focus on the major building structures,the paper makes statistical analysis on the earthquake damage ratio,loss ratio and seismic hazard index in the areas with different seismic intensity of the 50 events,and presents the seismic hazard matrix of buildings for the Yunnan area.

Location of high seismic activity zones and seismic hazard assessment in Zabrze Bielszowice coal mine using passive tomography

In the paper results of passive tomography calculations have been presented to assess rockburst hazard and locate high seismic activity zones in the vicinity of longwall 306 in Zabrze Bielszowice coal mine. The area of study was 1000 m in X direction by 900 m in Y direction. The zones of high values of P-wave propagation velocity have been found to correlate with the distribution of large seismic tremors.

Seismic hazard assessment of the Three Gorges Project

Seismic monitoring data for the past 50 years in the Three Gorges Reservoir area show that the reservoir head area is a typical weak seismic region with low seismieity before impoundment and that the epicenters were concentrated in the east and west sides of the Zigui Basin, most of which were natural tectonic earth- quakes. After impoundment, the seismic activity shifted to the segment between Badong and Zigui along the Yangtze River, mainly within 5 km of the reservoir bank. The seismogenesis was categorized into four types： Karst collapse earthquakes, earthquakes caused by Karst gas explosion, mining tunnel collapse earthquakes, and rock （terrane） slip earthquakes, all of which are related to the lithology, structure, and tectonics of near- surface geological bodies of the area. Compared with the seismicity before impoundment, the seismic frequency increase was remarkable, with most of the magnitudes below Ms2.0. Therefore, the intensity of the earth- quakes remained at a low level. On November 22, 2008, a magnitude 4.1 earthquake, the largest earthquake recorded since impoundment, occurred in Quyuan Town, Zigui County. The intensity and PGA of reservoir-in- duced earthquakes are higher than those of tectonic earthquakes with equal magnitude, but the peak intensity of reservoir-induced earthquakes is not likely to go beyond that of the estimated range from earlier studies.

Performance-based system seismic assessment for long-span suspension bridges under two-level seismic hazard

Since there are few studies on the performance-based seismic evaluation of the long-span suspension bridge system under two-level earthquake hazard in Chinese code,the developed procedure of this study can be regarded as a general program to assess the seismic performance of the overall system for long-span suspension bridges.In the procedure,the probabilistic seismic demand models of multiple bridge components were developed by nonlinear time-history analyses incorporating the related uncertainties,and the component-level fragility curves were calculated by the reasonable definition of limit states of the corresponding components in combination with seismic hazard analysis.The bridge repair cost ratios used to evaluate the system seismic performance were derived through the performance-based methodology and the damage probability of critical components.Furthermore,the repair cost ratios of the overall bridge system that was retrofitted with fluid viscous dampers for the main bridge and changed restraint systems for the approach bridges were compared.The results show that peak ground velocity and peak ground acceleration can be selected as the optimal intensity measurements of long-span suspension bridges using the TOPSIS(technique for order preference by similarity to an ideal solution).The bridge repair cost ratios can serve as accurate evaluation indicators to provide an efficient evaluation of retrofit measures.The seismic evaluation of long-span bridges is misled when ignoring the interaction of adjacent structures.However,the repair cost ratios of a bridge system that has optimum seismic performance are less sensitive to the relative importance of adjacent structures.

Probabilistic seismic hazard assessment of Kazakhstan and Almaty city in peak ground accelerations

As for many post-soviet countries, Kazakhstan’s building code for seismic design was based on a deterministic approach. Recently, Kazakhstan seismologists are engaged to adapt the PSHA(probabilistic hazard assessment) procedure to the large amount of available geological, geophysical and tectonic Kazakh data and to meet standard requirements for the Eurocode 8. The new procedure has been used within National projects to develop the Probabilistic GSZ(General Seismic Zoning) maps of the Kazakhstan territory and the SMZ(Probabilistic Seismic Microzoning) maps of Almaty city. They agree with the seismic design principles of Eurocode 8 and are expressed in terms of not only seismic intensity,but also engineering parameters(peak ground acceleration PGA). The whole packet of maps has been developed by the Institute of Seismology, together with other Kazakhstan Institutions. Our group was responsible for making analysis in PGA. The GSZ maps and hazard assessment maps for SMZ in terms of PGA for return periods 475 and 2475 years are considered in the article.

Probabilistic seismic hazard analysis in Nepal

The seismic ground motion hazard for Nepal has been estimated using a probabilistic approach. A catalogue of earthquakes has been compiled for Nepal and the surrounding region （latitude 26% N and 31.7% N and longitude 79° E and 90° E） from 1255 to 2011. The distribution of catalogued earthquakes, together with available geological and tectonic information were used to delineate twenty-three seismic source seismic source information and probabilistic earthquake hazard prediction relationship, peak ground accelerations （PGAs） have zones in Nepal and the surrounding region. By using the parameters in conjunction with a selected ground motion been calculated at bedrock level with 63%, 10%, and 2% probability of exceedance in 50 years. The estimated PGA values are in the range of 0.07-0.16 g, 0.21 0.62 g, and 0.38-1.1 g for 63%, 10%, and 2% probability of exceedance in 50 years, respectively. The resulting ground motion maps show different characteristics of PGA distribution, i.e., high hazard in the far-western and eastern sections, and low hazard in southern Nepal. The quantified PGA values at bedrock level provide information for microzonation studies in different parts of the country.

State of art of seismic design and seismic hazard analysis for oil and gas pipeline system

The purpose of this paper is to adopt the uniform confidence method in both water pipeline design and oil-gas pipeline design.Based on the importance of pipeline and consequence of its failure,oil and gas pipeline can be classified into three pipe classes,with exceeding probabilities over 50 years of 2%,5% and 10%,respectively.Performance-based design requires more information about ground motion,which should be obtained by evaluating seismic safety for pipeline engineering site.Different from a city＇s water pipeline network,the long-distance oil and gas pipeline system is a spatially linearly distributed system.For the uniform confidence of seismic safety,a long-distance oil and pipeline formed with pump stations and different-class pipe segments should be considered as a whole system when analyzing seismic risk.Considering the uncertainty of earthquake magnitude,the design-basis fault displacements corresponding to the different pipeline classes are proposed to improve deterministic seismic hazard analysis（DSHA）.A new empirical relationship between the maximum fault displacement and the surface-wave magnitude is obtained with the supplemented earthquake data in East Asia.The estimation of fault displacement for a refined oil pipeline in Wenchuan MS8.0 earthquake is introduced as an example in this paper.

Site specific probabilistic seismic hazard analysis at Dubai Creek on the west coast of UAE

A probabilistic seismic hazard analysis （PSHA） was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates （UAE）. The PSHA considered all the seismogenic sources that affect the site, including plate boundaries such as the Makran subduction zone, the Zagros fold-thrust region and the transition fault system between them; and local crustal faults in UAE. PSHA indicated that local faults dominate the hazard. The peak ground acceleration （PGA） for the 475-year return period spectrum is 0.17 g and 0.33 g for the 2,475-year return period spectrum. The hazard spectra are then employed to establish rock ground motions using the spectral matching technique.

Seismic Hazard Assessment of District Mansehra,Khyber Pakhtoonkhawa,Pakistan

The site of Mansehra is located seismically in an active regime, known as the Crystalline Nappe Zone and Hazara-Kashmir Syntaxis in NW Himalayas, Pakistan. Seismic Hazard Assessment （SHA） for the site has been carried out by considering the earthquake source zones, selection of appropriate attenuation equations, near fault effects and maximum potential magnitude estimation. The Mansehra Thrust, Oghi Fault, Banna Thrust, Balakot Shear Zone, Main Boundary Thrust, Panjal Thrust, Jhelum Fault and Muzaffarabad Fault and, further to the south, the Sanghargali, Nathiagali, and Thandiani Thrusts are the most critical tectonic features within the 50 km radius of Mansehra. Using the available instrumental seismological data from 1904 to 2007, SHA has been carried out. Other reactivated critical tectonic features in the area have been investigated. Among them the Balakot-Bagh fault, with the fault length of 120 km from Balakot to Poonch, has been considered as the most critical tectonic feature on the basis of geological/structural/seismological data. The potential earthquake of maximum magnitude 7.8 has been assigned to the Balakot-Bagh fault using four regression relations. The peak ground acceleration value of 0.25 g （10% probability of exceedance for 50 years） and 0.5 g has been calculated with the help of the attenuation equation using probabilistic and deterministic approaches.

Active Fault Exploration and Seismic Hazard Assessment in Fuzhou City

It has been proven by a number of earthquake case studies that an active fault-induced earthquake beneath a city can be devastating. It is an urgent issue for seismic hazard reduction to explore the distribution of active faults beneath the urban area and identify the seismic source and the risks underneath. As a pilot project of active fault exploration in China, the project, entitled “Active fault exploration and seismic hazard assessment in Fuzhou City”, started in early 2001 and passed the check before acceptance of China Earthquake Administration in August 2004. The project was aimed to solve a series of scientific issues such as fault location, dating, movement nature, deep settings, seismic risk and hazard, preparedness of earthquake prevention and disaster reduction, and etc. by means of exploration and assessment of active faults by stages, i.e., the preliminary survey and identification of active faults in target area, the exploration of deep seismotectonic settings, the risk evaluation of active seismogenic faults, the construction of geographic information system of active faults, and so on. A lot of exploration methods were employed in the project such as the detection of absorbed mercury, free mercury and radon in soil, the geological radar, multi-channel DC electrical method, tsansient electromagnetic method, shallow seismic refraction and reflection, effect contrast of explored sources, and various sounding experiments, to establish the buried Quaternary standard section of the Fuzhou basin. By summing up, the above explorations and experiments have achieved the following results and conclusions ：

Inferring seismic hazard in Sichuan-Yunnan region of China based on the modern earthquake catalogue (1980-2019)

Based on the modern earthquake catalogue,the incomplete centroidal voronoi tessellation(ICVT)method was used in this study to estimate the seismic hazard in Sichuan-Yunnan region of China.We calculated spatial distributions of the total seismic hazard and background seismic hazard in this area.The Bayesian delaunay tessellation smoothing method put forward by Ogata was used to calculate the spatial distributions of b-value.The results show that seismic hazards in Sichuan-Yunan region are high,and areas with relatively high hazard values are distributed along the main faults,while seismic hazards in Sichuan basin are relatively low.

Finite element simulation of stress change for the M_(S)7.4 Madoi earthquake and implications for regional seismic hazards

On May 22,2021,the M_(S)7.4 earthquake occurred in Madoi County,Qinghai Province;it was another strong event that occurred within the Bayan Har block after the Dari M_(S)7.7 earthquake in 1947.An earthquake is bound to cast stress to the surrounding faults,thus affecting the regional seismic hazard.To understand these issues,a three-dimensional viscoelastic finite element model of the eastern Bayan Har block and its adjacent areas was constructed.Based on the co-seismic rupture model of the Madoi earthquake,we analyzed the co-and postseismic Coulomb stress change caused by the Madoi earthquake on the surrounding major faults.The results show that the Madoi earthquake caused significant co-seismic stress increases in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault(>10 kPa),which exceeded the proposed threshold of stress triggering.By integrating the accumulation rate of the inter-seismic tectonic stress,we conclude that the Madoi earthquake caused future strong earthquakes in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault to advance by 55.6-623 and 24.7-123 a,respectively.Combined with the influence of the Madoi earthquake and the elapsed time of the last strong earthquake,these two segments have approached or even exceeded the recurrence interval of the fault prescribed by previous research.In the future,it is necessary to focus greater attention on the seismic hazard of the Maqin-Maqu and Tuosuo Lake segments.This study provides a mechanical reference to understand the seismic hazard of the East Kunlun fault in the future,particularly to determine the seismic potential region.

Seismic Hazard Assessment in the Boundary Region of Indo-China:First Phase of Implementation of the Global Seismic Hazard Assessment Program (GSHAP) in Continental Asia

The primary goal of the demonstration project endorsed by the Scientific and Technical Committee for IDNDR in 1992 is to ensure that national agencies are able to assess seismic hazard in a regionally coordinated fashion by using advanced methods.China,as a Regional Center of Central Southern Asia,has contacted with countries of the region to realistically practice seismic hazard assessments of Continental Asia.A test area located in the collision boundary between the Indian and Eurasian plates was chosen to examine the seismic hazard assessment approach in the regional coordinates.The seismotectonics and three versions of seismic sources of the test area are described in this paper and under the Global Seismic Hazard Assessment Program(GSHAP),guidelines an earthquake catalogue of the test area was assembled.Because of the incompleteness of earthquake data in different countries,we adopt different time windows for different magnitude intervals in order to obtain the seismicity parameters of sources.By

Seismic hazard analysis for central-western Argentina

In this study, we present a PSHA（Probabilistic Seismic Hazard Analysis） for the city of San Juan, which is located in the central-western region of Argentina（30°S-35.5°S; 66.5°W-71°W）. In addition to crustal earthquakes provided by catalogues, recent paleoseismological and neotectonic investigations have permitted to consider events which occurred during the last 400 years.Four seismogenic sources that could cause damages to the studied site corresponding to Precordillera,Western Sierras Pampeanas, Basement of the Cuyana Basin and Cordillera Principal were identified.Based on the evaluation of the contribution of these sources,maximum moment magnitudes above 7.5（Mw） are expected.High values of SA（spectral acceleration）（0.2 and 1 s periods） and PGA（peak ground acceleration） were found in the city of San Juan, which suggests that it is located in a zone of high seismic hazard.Finally, the obtained SA spectra were compared with the seismic-resistant construction standards of Argentina INPRES-CIRSOC 103 [1]. Results suggest that for the city of San Juan and for a return period of475 years, it covers the seismic requirements of the structures.

Effect of Aftershocks on Assessment of Seismic Hazard for Hebei Seismic Zone,China

In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the earthquake hazard estimation. The declustered catalogues have been compiled from the raw catalogues by deleting the aftershocks in different time interval after main shock according to the criteria for the aftershock activity period. As an example, Hebei seismic zone is taken to show the effect of the aftershock on the earthquake hazard assessment because three strong earthquakes with the aftershocks occurred from 1966 to 1976. The results have been shown that the effect of the aftershocks on the parameters λ m,b is significant. The difference between the clustered and declustered catalogues has reached in seismic activity rate and recurrence period, at most, 45% and 90%, respectively. But the difference in M max is smaller. Based on this, the suggestion that the aftershocks should be omitted in the estimation of the earthquake hazard could be made, but how long the aftershocks activity duration is still left to the future research.

Background Seismicity and Its Application to Seismic Hazard Assessment in the North China Region

The historical earthquake activity is intense in the North China region. However, no middle-sized earthquakes have occurred in the last decades in the region since the Ms6.2 earthquake in the Zhangbei region in 1998. The quiescence of moderate and strong earthquakes is quite prominent in North China. In this paper, we use small earthquake records in 1970 ~ 2009 to study background seismic activity in the North China region. The spatial distributions of seismic parameters are presented, including b-value, the maximum magnitude and annual occurrence probability of earthquakes of M/〉6. 0. Our results show regions with low b-value that include the Yuncheng region in the Shanxi rift, the Suqian region located in the Tancheng-Lujiang fault zone and the Shijiazhuang region in the Taihangshan block. Our analysis on the synthetic spatial pattern of seismicity indicate that seismicity in the North China region is mainly affected by the regional dynamic factors of deep structures.

Copula joint function and its application in probability seismic hazard analysis

A mature mathematical technique called copula joint function is introduced in this paper, which is commonly used in the financial risk analysis to estimate uncertainty. The joint function is generalized to the n-dimensional Frank’s copula. In addition, we adopt two attenuation models proposed by YU and Boore et al, respectively, and construct a two-dimensional copula joint probabilistic function as an example to illustrate the uncertainty treatment at low probability. The results show that copula joint function gives us a better prediction of peak ground motion than that resultant from the simple linear weight technique which is commonly used in the traditional logic-tree treatment of model uncertainties. In light of widespread application in the risk analysis from financial investment to insurance assessment, we believe that the copula-based technique will have a potential application in the seismic hazard analysis.

Potential rupture surface model and its ap-plication on probabilistic seismic hazard analysis

Potential sources are simplified as point sources or linear sources in current probabilistic seismic hazard analysis （PSHA） methods. Focus size of large earthquakes is considerable, and fault rupture attitudes may have great influence upon the seismic hazard of a site which is near the source. Under this circumstance, it is unreasonable to use the simplified potential source models in the PSHA, so a potential rupture surface model is proposed in this paper. Adopting this model, we analyze the seismic hazard near the Chelungpu fault that generated the Chi-Chi （Jiji） earthquake with magnitude 7.6 and the following conclusions are reached. （1） This model is reasonable on the base of focal mechanism, especially for sites near potential earthquakes with large magnitude; （2） The attitudes of potential rupture surfaces have great influence on the results of probabilistic seismic hazard analysis and seismic zoning.