Global Seismic Hazard Assessment Program Research Articles

Asian Seismological Commission — A Bright History and Challenges Ahead

The Asian Seismological Commission (ASC) completed 25 years in August 2021 after fulfilling its primary aim of bringing together, Earth scientists from Asia and Oceania regions. Since its first formal meeting in Tangshan, China during August 1–3, 1996 under the umbrella of IASPEI Regional Assembly, ASC independently organized 11 General Assemblies across the Asian Continent from Armenia and Iran in western Asia to Australia in Oceania, once every two years, without a break. The Training Courses in Seismology preceding these Assemblies greatly helped in developing a strong work force that came very handy after the extreme event of 2004 Indian Ocean tsunami and underlined the importance of scientific cooperation within Asian and Pacific Ocean countries. The Global Seismic Hazard Assessment Program (GSHAP) in its closing report to the IDNDR/STC (1992–98) acknowledged the significant contributions of the first two ASC technical meetings held in Beijing (10/93, 10/94) and Hyderabad, India (3/96) in the outcome of their program in Eastern Asia (GHSAP Region 8). This paper describes the ASC events that occurred during its journey from birth to reaching the pinnacle of its glory at the end of the Silver Jubilee Year in 2021. This paper will also serve as a recorded history for posterity to build upon the efforts already made, by the coming generations in this field.

Comparing Probabilistic Seismic Hazard Maps with ShakeMap Footprints for Indonesia

AbstractA number of probabilistic seismic hazard assessment (PSHA) maps have been released for Indonesia over the past few decades. This study proposes a method for testing PSHA maps using U.S. Geological Survey ShakeMap catalog considered as historical seismicity for Indonesia. It consists in counting the number of sites on rock soil for which the independent maximum peak ground acceleration (PGA) of the ShakeMap footprints between May 1968 and May 2018 exceeds the thresholds from the PSHA map studied and in comparing this number with the probability of exceedance given in the PSHA map. Although ShakeMap footprints are not as accurate and complete as continuous recorded ground motion, the spatially distributed ShakeMap covers 7,642,261 grid points, with a resolution of 1 km2, compensating the lack of instrumental data over this period. This data set is large enough for the statistical analysis of independent PGA values on rock sites only. To obtain the subdata set, we develop a new selection process and a new comparison method, considering the uncertainty of ShakeMap estimates. The method is applied to three PSHA maps (Global Seismic Hazard Assessment Program [GSHAP], Global Assessment Report [GAR], and Standar Nasional Indonesia [SNI2017]) for a selection of sites first located in Indonesia and next only in the western part of the country. The results show that SNI2017 provides the best fit with seismicity over the past 50 yr for both sets of rock sites (whole country and western part only). At the opposite, the GAR and GSHAP seismic hazard maps only fit the seismicity observed for the set of rock sites in western Indonesia. This result indicates that this method can only conclude on the spatial scale of the analysis and cannot be extrapolated to any other spatial resolution.

Review of Seismic Characteristics in Erbil City, the Capital of the Kurdistan Region of Iraq

Erbil city essentially suffers from the risk of earthquakes generated by Zagros-Taurus Belt. The central objective of this study is to identify the seismic characteristics and required seismic parameters for structural analysis. The methodology concentrated on reviewing the seismology and geology of Erbil city. It was concluded that the tectonically classified by an outer platform of the low folded zone in the position of Western Zagros Fold-Thrust Belt of the Arabian plate, geologically covered by Quaternary sediments and lithologically described by fluvial sediments, and the dynamic soil properties classified by site Class D. Seismicity review indicated that the seismic source is characterized by strike-slip (normal) fault and majority events exhibit at the shallow crustal with expected moment magnitude between 6 and 7.5. It was observed that the peak ground acceleration (PGA) has been updated, especially after the last cyclic earthquake in the region. The summary of the previous seismic hazard indicates that the PGA according to the World Health Organization, Global Seismic Hazard Assessment Program, and Uniform building code is identified by the value higher than 0.3 g for 475 years return period, while according to national probabilistic seismic hazard analysis studies in Iraq and Arabian Peninsula is identified by 0.4 g for 2% probability of exceedance in 50 years (2475 years return period), and estimated PGA to be 0.25 g for 10% likelihood of exceedance in 50 years (475 years return period), in a term of 5% damped at bedrock condition. Proposed spectral acceleration (Sa) in Erbil city at 0.2 and 1.0 s evaluated to be 1.0 g and 0.53 g, for the site Class D and compared with Sa in the literature.

Evaluation of ground motion and site-specific response spectrum for different parts of India by the method of semi-empirical Green’s function

A synthesis of ground motion and corresponding design response spectrum is presented here. A semi-empirical Green’s function approach based on envelope summation technique is used to model ground motion for evaluation of expected peak ground acceleration (PGA) from future large earthquake in Garhwal Himalaya, northeast (NE) and south India. The synthetic site-specific response spectra for the single degree of freedom (SDOF) structures corresponding to the synthetic ground motion records are obtained for both rock and soil conditions for engineering design of reservoir and nuclear power plant in different parts of India. The predicted PGA for NE India is found to be ~ 3.5 m/s2 at 60 km, decaying to ~ 0.1 m/s2 at 500 km distance, while it is ~ 3.0 m/s2 at 15 km, decaying to ~ 1.4 m/s2 at 80 km distance for Garhwal Himalaya. These PGA estimates are in good agreement with those obtained from the Global Seismic Hazard Assessment Program (GSHAP) exercise. The response spectrum attains its maximum relatively earlier for rock site than for soil site. The response spectra decay gradually at periods later than 0.5 s and approach asymptotically constant values at longer periods. The synthetic ground motions are used to perform seismic response analysis of engineering structures. For such analysis, a PGA of 0.027 g is estimated for the Tail pond reservoir in south India for a target earthquake of M 6.5 at 50 km distance, while a PGA of 0.015 g is found for the Gorakhpur nuclear power plant in north India for similar magnitude and distance. The difference in the PGA estimates between the two is mostly attributed to regional difference in attenuation and site response. The findings of this study are expected to facilitate the seismic design of engineered structures, safe from seismic hazard, in regions where strong motion data are sparse.

Earthquake Hazard and Risk Assessment Based on Unified Scaling Law for Earthquakes: State of Gujarat, India

The Gujarat state of India is one of the most seismically active intercontinental regions of the world. Historically, it has experienced many damaging earthquakes including the devastating 1819 Rann of Kachchh and 2001 Bhuj earthquakes. The effect of the later one is grossly underestimated by the Global Seismic Hazard Assessment Program (GSHAP). To assess a more adequate earthquake hazard for the state of Gujarat, we apply Unified Scaling Law for Earthquakes (USLE), which generalizes the Gutenberg–Richter recurrence relation taking into account naturally fractal distribution of earthquake loci. USLE has evident implications since any estimate of seismic hazard depends on the size of the territory considered and, therefore, may differ dramatically from the actual one when scaled down to the proportion of the area of interest (e.g. of a city) from the enveloping area of investigation. We cross-compare the seismic hazard maps compiled for the same standard regular grid 0.2° × 0.2° (1) in terms of design ground acceleration based on the neo-deterministic approach, (2) in terms of probabilistic exceedance of peak ground acceleration by GSHAP, and (3) the one resulted from the USLE application. Finally, we present the maps of seismic risks for the state of Gujarat integrating the obtained seismic hazard, population density based on India’s Census 2011 data, and a few model assumptions of vulnerability.

Reply to “Comment on ‘Total Probability Theorem Versus Shakeability: A Comparison between Two Seismic‐Hazard Approaches Used in Central Asia’ by D. Bindi and S. Parolai” by A. A. Gusev

The authors would like to thank Gusev (2016; hereafter referred to as Gu16) for his interest in our work (Bindi and Parolai, 2015; hereafter referred to as BP15) and for providing additional information about the methodology followed to prepare the hazard map for northern Eurasia included in the Global Seismic Hazard Assessment Program (GSHAP) model (Ulomov and the GSHAP region 7 Working Group, 1999, hereafter referred to as Ul99; Zhang et al. , 1999). The main interest of BP15 was to compare two probabilistic seismic‐hazard analysis approaches, namely the Riznichenko (1965) and the Cornell (1968, 1971) methods, which differ in the way they account for the aleatoric uncertainty. Although Gu16 agrees with the main conclusions of BP15 (“Another possible cause of the discussed discrepancy is certain difference between hazard calculation procedures of Riznichenko and Cornell. Both these observations of BP15 seem to be relevant, and need not be commented.”), he raises some criticisms against the discussions developed in BP15 regarding the GSHAP overestimation of the hazard level in central Asia (“Both assertments of BP15: that Ul99 hazard estimates are substantially exaggerated, and that this alleged fact is related to the use of Riznichenko (1965) procedures are incorrect.”). Here, it is worth remembering that, first, the overestimation of the Ul99 results is not an original statement of BP15, but, as also mentioned by Gu16, it was originally observed by Zhang et al. (1999) when compiling the GSHAP map, and, second, the Riznichenko approach followed in preparing the hazard map for northern Eurasia was a working hypothesis tested in BP15, not an absolute statement. Indeed, this hypothesis was inspired directly by Ul99 (“We calculate seismic hazard using an algorithm and software code designed by Gusev, Pavlov and Shumilina, following the principles of Riznichenko (1965) and Cornell (1968).”). Considering …

Comment on “Total Probability Theorem Versus Shakeability: A Comparison between Two Seismic‐Hazard Approaches Used in Central Asia” by D. Bindi and S. Parolai: Table 1

The recent paper of D. Bindi and S. Parolai (Bindi and Parolai, 2015; hereafter referred to as BP15) considers discrepancies between variants of seismic‐hazard estimates for central Asia. BP15 notes that for this territory the levels of hazard estimated in Ulomov et al. (1999; hereafter referred to as Ul99) during the construction of the Global Seismic Hazard Assessment Program (GSHAP) map shows a clear mismatch when compared with similar maps for neighboring areas: hazard estimates of Ul99 are systematically larger. Indeed, when Zhang et al. (1999) who were responsible for aggregating probabilistic seismic‐hazard assessment (PSHA) maps for various territories of Asia into the single final map tried to combine the component maps, the only way to incorporate the results of Ul99 was to decrease its peak ground acceleration (PGA) values by ∼30%. BP15 discusses the assumption that this problem could be caused by deficiencies of Riznichenko’s hazard estimation procedure, believed to be used in the calculating of Ul99 for GSHAP. The first deficiency under discussion is the implicit assumption of Riznichenko (1965) that the level of shaking, when considered as a function of magnitude M and distance r , can be treated in deterministic style, with no allowance for the scatter of individual observations with respect to an assumed mean relationship. Originally, Riznichenko expressed the level of shaking in terms of macroseismic intensity I , but most of the further discussion is applicable to cases when the level of shaking is expressed in any amplitude measure, further generically denoted A . The need to account for the scatter of I or A is evident (see e.g., Keilis‐Borok et al. , 1973). BP15 comes to the conclusion that their initial guess is untrue: the possible assumption of zero …

Global Seismic Hazard Assessment Program - GSHAP legacy

<p>Global Seismic Hazard Assessment Program - or simply GSHAP, when launched, almost two decades ago, aimed at establishing a common framework to evaluate the seismic hazard over geographical large-scales, i.e. countries, regions, continents and finally the globe. Its main product, the global seismic hazard map was a milestone, unique at that time and for a decade have served as the main reference worldwide. Today, for most of the Earth’s seismically active regions such Europe, Northern and Southern America, Central and South-East Asia, Japan, Australia, New Zealand, the GSHAP seismic hazard map is outdated. The rapid increase of the new data, advance on the earthquake process knowledge, technological progress, both hardware and software, contributed all in updates of the seismic hazard models. We present herein, a short retrospective overview of the achievements as well as the pitfalls of the GSHAP. Further, we describe the next generation of seismic hazard models, as elaborated within the Global Earthquake Model, regional programs: the 2013 European Seismic Hazard Model, the 2014 Earthquake Model for Middle East, and the 2015 Earthquake Model of Central Asia. Later, the main characteristics of these regional models are summarized and the new datasets fully harmonized across national borders are illustrated for the first time after the GSHAP completion.</p>

Too generous to a fault? Is reliable earthquake safety a lost art? Errors in expected human losses due to incorrect seismic hazard estimates

“One is well advised, when traveling to a new territory, to take a good map and then to check the map with the actual territory during the journey.” In just such a reality check, Global Seismic Hazard Assessment Program (GSHAP) maps (prepared using PSHA) portrayed a “low seismic hazard,” which was then also assumed to be the “risk to which the populations were exposed.” But time‐after‐time‐after‐time the actual earthquakes that occurred were not only “surprises” (many times larger than those implied on the maps), but they were often near the maximum potential size (Maximum Credible Earthquake or MCE) that geologically could occur. Given these “errors in expected human losses due to incorrect seismic hazard estimates” revealed globally in these past performances of the GSHAP maps (> 700,000 deaths 2001–2011), we need to ask not only: “Is reliable earthquake safety a lost art?” but also: “Who and what were the ‘Raiders of the Lost Art?’ ”

SP-064 RESULTS OF AUTOLOGOUS PERIPHERAL HEMATOPOIETIC STEM CELL TRANSPLANTATION FOR PATIENTS WITH MULTIPLE MYELOMA WITHOUT MAINTENANCE THERAPY

In the process of updating existing PSHA maps in Central Asia, a first step is the evaluation of the seismic hazard in terms of macroseismic intensity by applying a data driven method. Following the Site Approach to Seismic Hazard Assessment (SASHA) [11], the evaluation of the probability of exceedance of any given intensity value over a fixed exposure time, is mainly based on the seismic histories available at different locations without requiring any a-priori assumption about seismic zonation. The effects of earthquakes not included in the seismic history can be accounted by propagating the epicentral information through a Intensity Prediction Equation developed for the analyzed area. In order to comply with existing building codes in the region that use macroseismic intensity instead of PGA, we evaluated the seismic hazard at 2911 localities using a macroseismic catalog composed by 5322 intensity data points relevant to 75 earthquakes in the magnitude range 4.6–8.3. The results show that for most of the investigated area the intensity having a probability of at least 10% to be exceeded in 50 years is VIII. The intensity rises to IX for some area struck by strong earthquakes in the past, like the Chou-Kemin-Chilik fault zone in northern Tien-Shan, between Kyrgyzstan and Kazakhstan, or in Gissar range between Tajikistan and Uzbekistan. These values are about one intensity unit less than those evaluated in the Global Seismic Hazard Assessment Program (GSHAP; Ulomov, The GSHAP Region 7 working group [29]). Moreover, hazard curves have been extracted for the main towns of Central Asia and the results compared with the estimates previously obtained. A good agreement has been found for Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan), while a lower probability of occurrence of I=VIII has been obtained for Tashkent (Uzbekistan) and a larger one for I=IX in Almaty (Kazakhstan).

The 2013 Lushan Earthquake in China Tests Hazard Assessments

Online Material: Earthquake hazard map; figures showing geodynamic and elastic block models; and table of M s>6 earthquakes used in the study. Following the devastating 2008 Wenchuan earthquake that ruptured the central–northern segments of the Longmenshan fault in Sichuan, China, many studies assessed its impact on other major faults in this region (e.g., Parsons et al. , 2008; Toda et al. , 2008). On 20 April 2013, the M w 6.6 Lushan earthquake ruptured the southern segment of the Longmenshan fault, allowing these assessments to be tested. The 2008 Wenchuan earthquake ( M w 7.9) came as a surprise, because the Longmenshan fault zone, which separates the growing Tibetan Plateau from the rigid Sichuan basin (Fig. 1), slips slowly (less than 3 mm/yr; Shen et al. , 2009); with only moderate seismicity (Burchfiel et al. , 2008; Wang et al. , 2010). The earthquake‐hazard map by the Global Seismic Hazard Assessment Program shows the entire Longmenshan fault zone as being relatively safe, as shown in ![Graphic][1] Figure S1 (available in the electronic supplement to this paper). Figure 1. Topography (color contours), faults (lines), and seismicity (dots) of eastern Tibetan Plateau and Sichuan basin. Gray dots, historic events; red dots, instrumentally recorded events; beach ball, fault plane solution and aftershock sequence of the 2008 Wenchuan earthquake are in light blue; those for the 2013 Lushan earthquake are in dark blue. Epicenters are from the China Earthquake Data Center (http://data.earthquake.cn/data, last accessed April 2013). Inset map shows the location of the map region. The same cannot be said for the M w 6.6 Lushan earthquake, which occurred in the morning of … [1]: /embed/inline-graphic-1.gif

Geohazards assessment and mapping of some Balkan countries

The assessment of geological hazard is a topic with significant interest for the Balkans. During the last decade of twentieth century, most of the countries in the region have embarked on the road of a hasty transitory period from totalitarian regimes to democracy. Development of free market economy has given rise to uncontrolled movement of people, fast construction of housing and facilities and unproportioned accumulation of population around and in big cities. Besides Greece, an old member of European Union, and two newcomers in the organization, Romania and Bulgaria, the other countries are all hoping to enter the Union as faster as they can. Many different candidate or full-fledged member country programs of European Community offer a lot of joint and cross-border projects for constructing road infrastructure and facilities. As development accelerates in the Balkans and given the intensive geohazard elements that this territory exhibits, it becomes increasingly important to understand, study, and map these elements for being aware of the damage to the total environment these hazards might cause. The geohazard map and assessment of some Balkan countries has been carried out through two scientific meetings in Ohrid, Macedonia, and Tirana, Albania during 2007. The map is compiled in the Albanian Geological Survey, Tirana, Albania in the scale 1:1,000,000. As a base map, we used the topographic map produced by VGI, formerly Yugoslavia mapping authorities. As a seismic layer in our map, we used the values of peak ground acceleration obtained from Global Seismic Hazard Assessment Program. Two catalogs were constructed: The first one that contains the crustal earthquakes (hypocentral depth within first 70 km) and the second one that contains intermediate earthquakes (hypocentral depth below 70 km). This work is largely based on previous studies and investigations by earth scientists and specialists of each country comprised in this territory. In this respect, the map we constructed should be considered as a preliminary composite geohazard map with the possibility to be enriched and added with other new elements and data in the future.

Global Seismic Hazard Assessment Program maps are erroneous

The March 11, 2011 megathrust on the Pacific coast of the Tohoku Region, Japan, and its consequences once again confirmed the presence of evident problems in the conventional methodology of risk and earthquake loss evaluation. A systematic analysis shows that the results of the Global Seismic Hazard Assessment Program (GSHAP, 1992–1999) contradict the actual occurrence of strong earthquakes. In particular, since the publication of the GSHAP final results in 1999, all 60 earthquakes with magnitudes of 7.5 or higher were “surprises” for the GSHAP maps. Moreover, in half of the cases they were “big surprises,” when instead of the expected “light” or “moderate,” “significant” or even “total” destruction took place. All twelve of the deadliest earthquakes happened in 2000–2011 (total number of deaths exceeded 700000 people) prove that the GSHAP results, as well as underlying methodologies, are deeply flawed and, evidently, unacceptable for any critical risk assessments entitled to prevent disasters caused by earthquakes.

Seismic hazard assessment in Central Asia: Outcomes from a site approach

In the process of updating existing PSHA maps in Central Asia, a first step is the evaluation of the seismic hazard in terms of macroseismic intensity by applying a data driven method. Following the Site Approach to Seismic Hazard Assessment (SASHA) [11], the evaluation of the probability of exceedance of any given intensity value over a fixed exposure time, is mainly based on the seismic histories available at different locations without requiring any a-priori assumption about seismic zonation. The effects of earthquakes not included in the seismic history can be accounted by propagating the epicentral information through a Intensity Prediction Equation developed for the analyzed area. In order to comply with existing building codes in the region that use macroseismic intensity instead of PGA, we evaluated the seismic hazard at 2911 localities using a macroseismic catalog composed by 5322 intensity data points relevant to 75 earthquakes in the magnitude range 4.6–8.3. The results show that for most of the investigated area the intensity having a probability of at least 10% to be exceeded in 50 years is VIII. The intensity rises to IX for some area struck by strong earthquakes in the past, like the Chou-Kemin-Chilik fault zone in northern Tien-Shan, between Kyrgyzstan and Kazakhstan, or in Gissar range between Tajikistan and Uzbekistan. These values are about one intensity unit less than those evaluated in the Global Seismic Hazard Assessment Program (GSHAP; Ulomov, The GSHAP Region 7 working group [29]). Moreover, hazard curves have been extracted for the main towns of Central Asia and the results compared with the estimates previously obtained. A good agreement has been found for Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan), while a lower probability of occurrence of I=VIII has been obtained for Tashkent (Uzbekistan) and a larger one for I=IX in Almaty (Kazakhstan).

Site-specific earthquake response study for hazard assessment in Kolkata city, India

The assessment of local site effects on seismic ground motions is of great importance in earthquake engineering practice. Several destructive earthquakes in the past have demonstrated that the amplification of ground motion and associated damage to structures due to local site conditions is a significant consideration in earthquake hazard analysis. A recent paper published in this journal highlights the hazard posed by earthquakes in the megacity of Kolkata in India due to its seismic and geological settings. The seismic hazard assessment study speculates that the deep alluvial deposit in the city may increase the seismic hazard probably due to the amplification of the seismic energies. This paper focuses on the seismic response studies of the various soil strata (i.e. for local subsurface conditions) obtained from various construction sites in the city for predicted earthquake. It is very well recognized that site response studies (a part of seismic microhazard zonation for urban areas) are the first step towards performance-based foundation design or seismic risk analysis and mitigation strategy. One of the problems for carrying out site-specific study in Kolkata is the lack of recorded strong motion data in the city. Hence, this paper outlines a methodology to carry out site-specific study, where no strong motion data or seismic data are available. The methodology uses wavelet-based spectrum compatibility approach to generate synthetic earthquake motions and equivalent linear method for seismic site response analysis. The Mega City of Kolkata has been considered to explain the methodology. Seismic hazard zonation map by the Bureau of Indian Standards classifies the City of Kolkata as moderate seismic zone (Zone III) with a zone factor 0.16. On the other hand, GSHAP(Global Seismic Hazard Assessment Program) map which is based on 10% probability of exceedance in 50 years specifies a maximum peak ground acceleration (PGA) of 1.6 m/s2 (0.163 g) for this region. In the present study, the seismic response has been carried out based on GSHAP. The results of the analysis indicate the amplification of ground motion in the range of 4.46–4.82 with the fundamental period ranging from 0.81 to 1.17 s. Furthermore, the maximum spectral accelerations vary in the range of 0.78–0.95 g.

Seismotectonic Models for South Africa: Synthesis of Geoscientific Information, Problems, and the Way Forward

should be reviewed; surface and subsurface investigations of the orientation, geometry, sense of displacement, and length of ruptures should be conducted; and the possibility of multiple ruptures ought to be assessed. Seismotectonic models have not yet been developed for South Africa. The delineation of seismotectonic zones of Africa as part of the Global Seismic Hazard Assessment Program (GSHAP) in 1999 was based on an analysis of the main tectonic structures and a correlation with present-day seismicity. Because of the large scale of the GSHAP project, only regional structures were accounted for in the preparation of the source zones. Our study was initiated to remedy this knowledge gap. We have completed four steps, which are described in this paper. Compilation of a catalog of earthquake activity that has

Seismic hazard scenario and attenuation model of the Garhwal Himalaya using near-field synthesis from weak motion seismometry

In this paper, we present a seismic hazard scenario for the Garhwal region of the north-western Himalayan range, in terms of the horizontal Peak Ground Acceleration. The scenario earthquake of moment magnitude Mw 8.5 has a 10% exceedance probability over the next 50 years. These estimates, the first for the region, were calculated through a stepwise process based on: An estimation of the Maximum Credible Earthquake from the seismicity of the region and Global Seismic Hazard Assessment Program considerations, and four seismotectonic parameters abstracted from near field weak-motion data recorded at five stations installed in Chamoli District of the Garhwal region in the aftermath of the 1999 Chamoli earthquake. The latter include The frequency dependent power law for the shear wave quality factor, QS the site amplification at each station using horizontal-to-vertical-spectral ratio and generalized inversion technique source parameters of various events recorded by the array and application of the resulting relations between the scalar seismic moment M0 (dyne-cm) and moment magnitude Mw and the corner frequency, ƒc (Hz) and moment magnitude Mw to simulate spectral acceleration due to higher magnitude events corresponding to the estimated Maximum Credible Earthquake, and regional and site specific local spectral attenuation relations at different geometrically central frequencies in the low, moderate and high frequency bands.

Probabilistic seismic hazard analysis for Bangalore

This article presents the results of probabilistic seismic hazard analysis (PSHA) for Bangalore, South India. Analyses have been carried out considering the seismotectonic parameters of the region covering a radius of 350 km keeping Bangalore as the center. Seismic hazard parameter ‘b’ has been evaluated considering the available earthquake data using (1) Gutenberg–Richter (G–R) relationship and (2) Kijko and Sellevoll (1989, 1992) method utilizing extreme and complete catalogs. The ‘b’ parameter was estimated to be 0.62 to 0.98 from G–R relation and 0.87 ± 0.03 from Kijko and Sellevoll method. The results obtained are a little higher than the ‘b’ values published earlier for southern India. Further, probabilistic seismic hazard analysis for Bangalore region has been carried out considering six seismogenic sources. From the analysis, mean annual rate of exceedance and cumulative probability hazard curve for peak ground acceleration (PGA) and spectral acceleration (Sa) have been generated. The quantified hazard values in terms of the rock level peak ground acceleration (PGA) are mapped for 10% probability of exceedance in 50 years on a grid size of 0.5 km × 0.5 km. In addition, Uniform Hazard Response Spectrum (UHRS) at rock level is also developed for the 5% damping corresponding to 10% probability of exceedance in 50 years. The peak ground acceleration (PGA) value of 0.121 g obtained from the present investigation is slightly lower (but comparable) than the PGA values obtained from the deterministic seismic hazard analysis (DSHA) for the same area. However, the PGA value obtained in the current investigation is higher than PGA values reported in the global seismic hazard assessment program (GSHAP) maps of Bhatia et al. (1999) for the shield area.

One Hundred Years of Earthquake Recording in Australia

Abstract A comprehensive new catalog of Australian earthquakes has been compiled and used to review the seismicity of Australia. The catalog contains 27,000 events, of which 17,000 are considered to be mainshocks. The catalog is complete for all Australian events with a magnitude greater than M L 5.5 since 1910, M L 5 since 1960, M L 4 since 1970, and M L 3.5 since 1980. It is complete for events in southern Australia above M L 3.5 since 1965 and M L 2 since 1980. Before the development of local magnitude scales for Australia, around 1990, the Richter magnitude scale was generally used. At 600 km (a typical hypocentral distance for much of Australia) the Richter formula overestimates magnitude by around 0.5 units. Thus, the results in the catalogs before and after the early 1990s are potentially discrepant. Most well-located Australian earthquakes are in the southern areas of the continent, where the seismometer density is greatest. In general, the location uncertainty of Australian earthquakes is high. Only 60% of events are located with an uncertainty of 10 km or less. This percentage is smaller for earthquakes before 1980, and before 1960 very few events were located to within 10 km. The hypocentral depths of Australian earthquakes range mostly between 8 and 18 km, except for the southwest corner of the continent where they are typically shallower than 5 km. The seismicity in some areas of Australia has been steady for at least 100 yr (including the southeast corner, the Flinders Ranges, and the northwest corner). In contrast, seismicity in the southwest corner jumped by at least a factor of 6 in the 1940s and has been steady since then. Much of the rest of Australia is characterized by episodic seismicity. These episodes begin with a period of high activity lasting 1–10 yr and they are normally associated with a large ( M >6) earthquake. Following the large earthquake, there is often a period of moderate activity lasting from a few years to several decades. Before and after each episode is a quiescent period of low activity lasting 0.1–10 ka, during which the seismicity is more than an order of magnitude lower than during the period of high activity. Frequency-magnitude relations were calculated using events since 1970 from the new catalog. Gutenberg–Richter a - and b -values were calculated on an 85-km grid, and maps of the probability of an earthquake of M ≥4.9 occurring per year were derived. These results are very similar to the Global Seismic Hazard Assessment Program (GSHAP) map for Australia. The results were used to define four large (>20,000 km 2 ) seismogenic zones (Fig. 1). There are also several other small zones, some of which appear to reflect recent episodes, while others appear to be long-lived. The expected number of earthquakes M ≥5 and M ≥6, strain rate, and deformation rate is given for the four large zones, the remainder of Australia, and the whole Australian continent. The combined estimates of strain using seismic Global Positioning System (GPS) and Satellite Laser Ranging (SLR) data suggest east–west compressive deformation across southern Australia of 0.65±2.0 mm per year, likely to be in the 0.5–1.0-mm-per-year range.

Recorded Maximum Seismic Intensity Maps in Japan from 1586 to 2004

To evaluate the occurrence of large earthquakes and associated damaging ground motions, probabilistic ground-motion maps have been published for the United States, Japan, and other countries (Frankel et al. , 1996; Headquarters for Earthquake Research Promotion, 2005; Global Seismic Hazard Assessment Program, 1999). These maps are constructed by combining large amounts of data and model estimates of seismicity, distance attenuation, and local site response. A complementary map of maximum ground motion (intensity) also can be constructed empirically from a good record of historical intensity, for example, the compiled reports in Japan. Some past studies have used seismic intensities from historical earthquakes to quantify the expected level of strong shaking for Japan. Kawasumi (1951) used relations among intensity, magnitude, and acceleration to estimate expected maximum acceleration levels across Japan for periods of 75, 100, and 200 years. Kanai and Suzuki (1968), following a similar method, estimated peak velocity distributions. In another study of probabilistic hazards for Japan related to seismic intensities, Wesnousky et al. (1984) investigated the relationship among repeat times of earthquakes, seismic moment, and associated seismic intensity distribution using geologic-fault data and showed the probabilistic occurrence of earthquakes with intensity equal to or larger than JMA 5. However, the published probabilistic maps all depend largely on the models and inferences about the magnitudes and locations of historical earthquakes, which are diffi cult to verify fully. In this study we take the simple approach of directly mapping the maximum historical intensity distribution across Japan. We use the Japan Meteorological Agency (JMA) intensity, as observed by JMA and interpreted by Usami (2003). Historical records of earthquake damage in Japan extend back more than 1,000 years and provide a valuable resource for studying historical seismicity. We make no assumptions about earthquake location, magnitude-intensity relations, or earthquake occurrence models. This approach …