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1.
The Iranian Plateau does not appear to be a single crustal block, but an assemblage of zones comprising the Alborz—Azerbaijan, Zagros, Kopeh—Dagh, Makran, and Central and East Iran. The Gumbel’s III asymptotic distribution method (GIII) and maximum magnitude expected by Kijko—Sellevoll method is applied in order to check the potentiality of the each seismogenic zone in the Iranian Plateau for the future occurrence of maximum magnitude (Mmax). For this purpose, a homogeneous and complete seismicity database of the instrumental period during 1900–2012 is used in 29 seismogenic zones of the examined region. The spatial mapping of hazard parameters (upper bound magnitude (ω), most probable earthquake magnitude in next 100 years (M100) and maximum magnitude expected by maximum magnitude estimated by Kijko—Sellevoll method (max MK ? Smax) reveals that Central and East Iran, Alborz and Azerbaijan, Kopeh—Dagh and SE Zagros are a dangerous place for the next occurrence of a large earthquake.  相似文献   

2.
The maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of NW Himalaya and the adjoining regions. For this purpose, we have prepared a reliable, homogeneous and complete earthquake catalogue during the period 1500–2010. The technique used here allows the data to contain either historical or instrumental era or even a combination of the both. In this study, the earthquake hazard parameters, which include maximum regional magnitude (M max), mean seismic activity rate (λ), the parameter b (or β?=?b/log e) of Gutenberg–Richter (G–R) frequency-magnitude relationship, the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900–2010. The uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters. The earthquake hazard in the whole NW Himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level, tectonics and focal mechanism. The annual probability of exceedance of earthquake (activity rate) of certain magnitude is also calculated for all seismogenic source zones. The obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters. It is observed that seismic hazard level is high in Quetta-Kirthar-Sulaiman region in Pakistan, Hindukush-Pamir Himalaya region and Uttarkashi-Chamoli region in Himalayan Frontal Thrust belt. The source zones that are expected to have maximum regional magnitude (M max) of more than 8.0 are Quetta, southern Pamir, Caucasus and Kashmir-Himanchal Pradesh which have experienced such magnitude of earthquakes in the past. It is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity.  相似文献   

3.
A straightforward Bayesian statistic is applied in five broad seismogenic source zones of the northwest frontier of the Himalayas to estimate the earthquake hazard parameters (maximum regional magnitude M max, β value of G–R relationship and seismic activity rate or intensity λ). For this purpose, a reliable earthquake catalogue which is homogeneous for M W ≥ 5.0 and complete during the period 1900 to 2010 is compiled. The Hindukush–Pamir Himalaya zone has been further divided into two seismic zones of shallow (h ≤ 70 km) and intermediate depth (h > 70 km) according to the variation of seismicity with depth in the subduction zone. The estimated earthquake hazard parameters by Bayesian approach are more stable and reliable with low standard deviations than other approaches, but the technique is more time consuming. In this study, quantiles of functions of distributions of true and apparent magnitudes for future time intervals of 5, 10, 20, 50 and 100 years are calculated with confidence limits for probability levels of 50, 70 and 90 % in all seismogenic source zones. The zones of estimated M max greater than 8.0 are related to the Sulaiman–Kirthar ranges, Hindukush–Pamir Himalaya and Himalayan Frontal Thrusts belt; suggesting more seismically hazardous regions in the examined area. The lowest value of M max (6.44) has been calculated in Northern-Pakistan and Hazara syntaxis zone which have estimated lowest activity rate 0.0023 events/day as compared to other zones. The Himalayan Frontal Thrusts belt exhibits higher earthquake magnitude (8.01) in next 100-years with 90 % probability level as compared to other zones, which reveals that this zone is more vulnerable to occurrence of a great earthquake. The obtained results in this study are directly useful for the probabilistic seismic hazard assessment in the examined region of Himalaya.  相似文献   

4.
—The maximum likelihood estimation of earthquake hazard parameters has been made in the Himalayas and its surrounding areas on the basis of a procedure which utilizes data containing complete files of the most recent earthquakes. The entire earthquake catalogue used covers the period from 1900–1990. The maximum regional magnitude M max?, the activity rate of the seismic event λ, the mean return period R of earthquakes with a certain lower magnitude M max≥ m along with their probability of occurrence, as well as the parameter b of of Gutenberg Richter magnitude-frequency relationship, have been determined for six different seismic zones of the Himalayas and its vicinity. It is shown that in general the hazard is higher in the zone NEI and BAN than the other four zones. The high difference of the b parameter and the hazard level from zone to zone reflect the high seismotectonic complexity and crustal heterogeneity.  相似文献   

5.
An endeavor is made to compute peak ground horizontal accelerations at bedrock level in the Delhi region due to the seismogenic sources present around Delhi. The entire area is divided into six seismogenic sources for which seismic hazard analysis is carried out using the complete and extreme part of the seismicity data. Maximum likelihood estimates of hazard parameters viz., seismic activity rate , b value and maximum probable earthquake M max are made for each zone. The return periods and the probabilities of occurrence of various magnitudes for return periods of 50, 100 and 1000 years are also computed for each zone. The peak ground acceleration (PGA) values for 20% exceedance in 50 years are then computed for the Delhi region from each zone. The maximum PGA value considering all the zones is 0.34 g, which is due to the Mathura fault zone. The seismogenic zones V and VI, i.e., Mathura fault zone and the Sohna fault zone are observed to be contributing maximum PGA values in the Delhi region governing the isoacceleration contours computed for the region. The seismic zonation map for the PGA values at the bedrock level is obtained for the Delhi region. This can be used directly as input for the microzonation of ground motion at the surface by incorporating the local site conditions.  相似文献   

6.
It is often assumed in probabilistic seismic hazard analysis that the magnitude distribution has an upper limit M max, which indicates a limitation on event size in specific seismogeneic conditions. Accurate estimation of M max from an earthquake catalog is a matter of utmost importance. We compare bias, dispersion and computational properties of four popular M max estimators, introduced by Kijko and others (e.g., Kijko and Sellevoll 1989, Kijko and Graham 1998, Kijko 2004) and we recommend the ones which can be the most fruitful in practical applications. We provide nomograms for evaluation of bias and standard deviation of the recommended estimators for combinations of sample sizes and distribution parameters. We suggest to use the bias nomograms to correct the M max estimates. The nomograms of standard deviation can be used to determine minimum sample size for a required accuracy of M max.  相似文献   

7.
Iranian earthquakes, a uniform catalog with moment magnitudes   总被引：3，自引：1，他引：2  
A uniform earthquake catalog is an essential tool in any seismic hazard analysis. In this study, an earthquake catalog of Iran and adjacent areas was compiled, using international and national databanks. The following priorities were applied in selecting magnitude and earthquake location: (a) local catalogs were given higher priority for establishing the location of an earthquake and (b) global catalogs were preferred for determining earthquake magnitudes. Earthquakes that have occurred within the bounds between 23–42° N and 42–65° E, with a magnitude range of M W 3.5–7.9, from the third millennium BC until April 2010 were included. In an effort to avoid the “boundary effect,” since the newly compiled catalog will be mainly used for seismic hazard assessment, the study area includes the areas adjacent to Iran. The standardization of the catalog in terms of magnitude was achieved by the conversion of all types of magnitude into moment magnitude, M W, by using the orthogonal regression technique. In the newly compiled catalog, all aftershocks were detected, based on the procedure described by Gardner and Knopoff (Bull Seismol Soc Am 64:1363–1367, 1974). The seismicity parameters were calculated for the six main tectonic seismic zones of Iran, i.e., the Zagros Mountain Range, the Alborz Mountain Range, Central Iran, Kope Dagh, Azerbaijan, and Makran.  相似文献   

8.
Historical seismic data and seismogenic information are quite scarce for the low seismicity region, and modeling the parameters uncertainties based on probabilistic model is suspicious. The convex set theory-based seismic hazard analysis approach is proposed. The uncertainties of b value, the annual occurrence rate v and the upper bound magnitude Mu are described by the envelop bound convex model and the ellipsoidal bound convex model. Convex analysis method and China probabilistic seismic hazard analysis methodology are combined to perform a bound seismic hazard analysis for Ningbo city, China. The seismic intensity interval obtained using the bound seismic hazard analysis is compared with that calculated using China probabilistic seismic hazard analysis methodology. The sensitivity analysis indicates that the interval of seismic intensity is most sensitive to the annual occurrence rate v. Furthermore, the different convex models have little effect on the interval of seismic intensity.  相似文献   

9.
—A seismogenic zoning for north Algeria is proposed. The characteristics of each zone are studied in detail and different statistical analyses are performed in order to assess the slope of the Gutenberg-Richter relationship, the mean annual activity rate of earthquakes, the average return period, the probability of non-exceedence during a time period and the maximum expected magnitude. The slope of the Gutenberg-Richter relationship determined by traditional methods, physical strain energy release and corresponding magnitude, together with a new approach based on both historical and instrumental data, are used to estimate the seismic hazard parameters.¶The seismic hazard parameters obtained described well the characteristics of each proposed seismogenic zone. The b-value of the Gutenberg-Richter relationship concurs especially well with the most common seismotectonic interpretation of each zone, for example 0.70 ± 0.06 at El Asnam region and 0.63 ± 0.09 around Algiers. The average return period obtained (approximately 300 years for magnitude 7.5 at El Asnam region, exceeding 1000 years in other regions), corroborate those obtained through Paleoseismic studies and others using a digital elevation model.  相似文献   

10.
The aim of this study is to investigate the seismicity of Central Anatolia, within the area restricted to coordinates 30–35° longitude and 38–41° latitude, by determining the “a” and “b” parameters in a Gutenberg–Richter magnitude–frequency relationship using data from earthquakes of moment magnitude (Mw)?≥?4.0 that occurred between 1900 and 2010. Based on these parameters and a Poisson model, we aim to predict the probability of other earthquakes of different magnitudes and return periods (recurrence intervals). To achieve this, the study area is divided into six seismogenic zones, using spatial distributions of earthquakes greater than Mw?≥?4.0 with active faults. For each seismogenic zone, the a and b parameters in the Gutenberg–Richter magnitude–frequency relationship were calculated by the least squares method. The probability of occurrence and return periods of various magnitude earthquakes were calculated from these statistics using the Poisson method.  相似文献   

11.
In this work, we reappraise the seismogenic potential of the geologic structures in the western Tell Atlas of Algeria, considered active host to moderate to low magnitude earthquakes. The direct identification of active faults is generally a difficult task in northern Algeria. The active tectonics in the Oran Plio-Quaternary age basin (Northwestern Algeria) is analyzed and characterized through a morpho-structural study combining topographic, geomorphologic, geological, and neotectonic data. Folds and fault scarps affecting Quaternary deposits show that the region is affected by compressional deformation still active nowadays, as shown by the recorded seismic activity. Our new observations enable a better understanding of the present seismotectonic context of the Oran region, particularly with regard to the magnitude and source of the 1790 Oran damaging event. The obtained result helps to shed some light on the elusive active tectonics characterizing this coastal area, and to assess regional seismic hazard, particularly in coastal zones where large seismogenic areas straddle the onshore–offshore zones.  相似文献   

12.
Probabilistic seismic hazard analysis (PSHA) has been carried out for Iraq. The earthquake catalogue used in the present study covers an area between latitude 29°–38.5° N and longitude 39°–50° E containing more than a thousand events for the period 1905–2000. The entire Iraq region has been divided into thirteen seismogenic sources based on their seismic characteristics, geological setting and tectonic framework. The completeness of the seismicity catalogue has been checked using the method proposed by Stepp (1972). The analysis of completeness shows that the earthquake catalogue is not complete below Ms=4.8 for all of Iraq and seismic source zones S1, S4, S5, and S8, while it varies for the other seismic zones. A statistical treatment of completeness of the data file was carried out in each of the magnitude classes. The Frequency Magnitude Distributions (FMD) for the study area including all seismic source zones were established and the minimum magnitude of complete reporting (Mc) were then estimated. For the entire Iraq the Mc was estimated to be about Ms=4.0 while S11 shows the lowest Mc to be about Ms=3.5 and the highest Mc of about Ms=4.2 was observed for S4. The earthquake activity parameters (activity rate , b value, maximum regional magnitude mmax) as well as the mean return period (R) with a certain lower magnitude mmin m along with their probability of occurrence have been determined for all thirteen seismic source zones of Iraq. The maximum regional magnitude mmax was estimated as 7.87 ± 0.86 for entire Iraq. The return period for magnitude 6.0 is largest for source zone S3 which is estimated to be 705 years while the smallest value is estimated as 9.9 years for all of Iraq.The large variation of the b parameter and the hazard level from zone to zone reflects crustal heterogeneity and the high seismotectonic complexity. The seismic hazard near the source boundaries is directly and strongly affected by the change in the delineation of these boundaries. The forces, through which the geological structure along the plate boundary in Eastern and Northeastern Iraq are evolved, are still active causing stress-strain accumulation, deformation and in turn producing higher probabilities of earthquake activity. Thus, relatively large destructive earthquakes are expected in this region. The study is intended to serve as a reference for more advanced approaches and to pave the path for the probabilistic assessment of seismic hazard in this region.  相似文献   

13.
Neo-deterministic seismic hazard assessment in North Africa   总被引：2，自引：2，他引：0  
North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2?×?0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D max), maximum velocity (V max), and design ground acceleration.  相似文献   

14.
In this work we review earthquakes that happened in Southern Siberia and Mongolia within the coordinates of 42°–62° N and 80°–124° E and first propose relationships between earthquake parameters (a surface-wave earthquake magnitude M s and an epicentral intensity(I 0) based on the MSK-64 scale) and maximal distances from an earthquake epicenter (R e max), hypocenter (R h max), and a seismogenic fault (R f max) to the localities of secondary coseismic effects. Special attention was paid to the study of these relationships for the effects of soil liquefaction. Hence, it was shown that secondary deformations from an earthquake were distributed in space away from an earthquake epicenter, than from an associating seismogenic fault. The effects of soil liquefaction are manifested by several times closer to a seismogenic fault, than all other effects, regardless of the type of tectonic movement in a seismic focus. Within the 40 km zone from an earthquake epicenter 44% of the known manifestations of liquefaction process occurred; within the 40 km zone from a seismogenic fault—90%. We propose the next relationship for effects of soil liquefaction: M s = 0.007 × R e max + 5.168 that increases the limits of the maximum epicentral distance at an earthquake magnitude of 5.2 ≤ M s ≤ 8.1 as compared to the corresponding relationships for different regions of the world.  相似文献   

15.
A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40–83° N and 20–40° E) includes 36,563 earthquake events, which are reported as 4.0–8.3 moment magnitude (MW) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude MW. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.  相似文献   

16.
We have studied the characteristics of the active faults and seismicity in the vicinity of Urumqi city, the capital of Xinjiang Autonomous Region, China, and have proposed a seismogenic model for the assessment of earthquake hazard in this area. Our work is based on an integrated analysis of data from investigations of active faults at the surface, deep seismic reflection soundings,seismic profiles from petroleum exploration, observations of temporal seismic stations, and the precise location of small earthquakes. We have made a comparative study of typical seismogenic structures in the frontal area of the North Tianshan Mountains, where Urumqi city is situated,and have revealed the primary features of the thrust-foldnappe structure there. We suggest that Urumqi city is comprised two zones of seismotectonics which are interpreted as thrust-nappe structures. The first is the thrust nappe of the North Tianshan Mountains in the west, consisting of the lower(root) thrust fault, middle detachment,and upper fold-uplift at the front. Faults active in the Pleistocene are present in the lower and upper parts of this structure, and the detachment in the middle spreads toward the north. In the future, M7 earthquakes may occur at the root thrust fault, while the seismic risk of frontal fold-uplift at the front will not exceed M6.5. The second structure is the western flank of the arc-like Bogda nappe in the east,which is also comprised a root thrust fault, middle detachment, and upper fold-uplift at the front, of which the nappe stretches toward the north; several active faults are also developed in it. The fault active in the Holocene is called the South Fukang fault. It is not in the urban area of Urumqi city. The other three faults are located in the urban area and were active in the late Pleistocene. In these cases,this section of the nappe structure near the city has an earthquake risk of M6.5–7. An earthquake M_S6.6, 60 km east to Urumqi city occurred along the structure in 1965.  相似文献   

17.
—?The maximum possible (regional) magnitude Mmax and other seismic hazard parameters like β which is the slope of Gutenberg-Richter law, and λ which is the intensity (rate) of seismic activity are estimated in eight seismic regions of the west side of the circum-Pacific belt. The Bayesian approach, as described by (Pisarenko et?al., 1996; Pisarenko and Lyubushin, 1997, 1999) is a straightforward technique of estimating the seismic hazard. The main assumptions for the method applied are a Poissonian character of seismic events flow, a frequency-magnitude law of Gutenberg-Richter's type with cutoff maximum value for the estimated parameter and a seismic catalog, which have a rather sizeable number of events. We also estimated the quantiles of the probabilistic distribution of the “apparent” Mmax for future given time-length intervals.  相似文献   

18.
Estimation of Maximum Earthquakes in Northeast India   总被引：1，自引：0，他引：1  
We attempt to estimate possible maximum earthquakes in the northeast Indian region for four seismic source zones, namely EHZ, MBZ, EBZ, and SHZ, which encapsulates the various seismogenic structures of the region and also for combined source zones taken as a single seismic source regime. The latter case exhibits a high maximum earthquake estimate of MW 9.4 (±0.85) through Bayesian interpretation of frequency magnitude distribution with Gamma function implicating a moderate deviation from the standard Gutenberg Richter model at the higher magnitudes. However, tapering Gutenberg Richter models with corner magnitudes at MW 8.01, 8.7 and 9.1, respectively indicated maximum values corresponding to MW 8.4, 9.0, and 9.3. The former approach was applied to each of the source zones wherein the data are presented in parts according to the data completeness, thereof. EHZ, MBZ, EBZ and SHZ are seen with maximum earthquakes of MW 8.35 (±0.59), 8.79 (±0.31), 8.20 (±0.50), and 8.73 (±0.70), respectively. The maximum possible earthquakes estimated for each individual zone are seen to be lower than that estimated for the single regime. However, the pertaining return periods estimated for the combined zone are far less than those estimated for the demarcated ones.  相似文献   

19.
—?Earthquake hazard parameters are estimated by the application of the maximum likelihood method. The technique is based on a procedure which utilizes data of different quality, e.g., those in which the uncertainty in the assessment of the magnitudes is great and those in which the magnitudes are computed with great precision. In other words the data were extracted from both historical (incomplete) and recorded (complete) files. The historical part of the catalogue contains only the strongest events, whereas the complete part can be divided into several sub-catalogues; each one assumed to be complete above a specified magnitude threshold. Uncertainty in the determination of magnitudes has also been taken into account. The method allows us to estimate the earthquake hazard parameters which are the maximum regional magnitude, M max, the activity rate, λ, of the seismic events and the well known value β (b=β?log?e), which is the slope of the magnitude-frequency relationship. All these parameters are of physical significance. The mean return periods, RP, of earthquakes with a certain lower magnitude M?≥?m are also determined. The method is applied in the Island of Crete and the adjacent area, where catastrophic earthquakes are known from the historical era. The earthquake hazard of the whole area is divided in a cellular manner which allow the analysis of the localized hazard parameters and the representation of their regional variation. The seismic hazard analysis, which is expressed by: (a) The annual probability of exceedance of a specified value of magnitude and (b) the return periods (in years) that are expected for given magnitudes, for shallow events is finally performed for shallow events. This hazard analysis is useful for both theoretical and practical reasons and provides a tool for earthquake resistant design in both areas of low and high seismicity.  相似文献   

20.
Evaluating Tsunami Hazard in the Northwestern Indian Ocean   总被引：1，自引：0，他引：1  
We evaluate here the tsunami hazard in the northwestern Indian Ocean. The maximum regional earthquake calculated from seismic hazard analysis, was used as the characteristic earthquake for our tsunami hazard assessment. This earthquake, with a moment magnitude of M w 8.3 and a return period of about 1000 years, was moved along the Makran subduction zone (MSZ) and its possible tsunami wave height along various coasts was calculated via numerical simulation. Both seismic hazard analysis and numerical modeling of the tsunami were validated using historical observations of the Makran earthquake and tsunami of the 1945. Results showed that the possible tsunami may reach a maximum height of 9.6 m in the region. The distribution of tsunami wave height along various coasts is presented. We recommend the development of a tsunami warning system in the region, and emphasize the value of education as a measure to mitigate the death toll of a possible tsunami in this region.  相似文献   

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