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1.
Öncel  A. O.  Alptekin  Ö. 《Natural Hazards》1999,19(1):1-11
In order to investigate the effect of aftershocks on earthquake hazard estimation, earthquake hazard parameters (m, b and Mmax) have been estimated by the maximum likelihood method from the main shocks catalogue and the raw earthquakes catalogue for the North Anatolian Fault Zone (NAFZ). The main shocks catalogue has been compiled from the raw earthquake catalogue by eliminating the aftershocks using the window method. The raw earthquake catalogue consisted of instrumentally detected earthquakes between 1900 and 1992, and historical earthquakes that occurred between 1000–1900. For the events of the mainshock catalogue the Poisson process is valid and for the raw earthquake catalogue it does not fit. The paper demonstrates differences in the hazard outputs if on one hand the main catalogues and on the other hand the raw catalogue is used. The maximum likelihood method which allows the use of the mixed earthquake catalogue containing incomplete (historical) and complete (instrumental) earthquake data is used to determine the earthquake hazard parameters. The maximum regional magnitude (Mmax, the seismic activity rate (m), the mean return period (R) and the b value of the magnitude-frequency relation have been estimated for the 24°–31° E, 31°–41° E, 41°–45° E sections of the North Anatolian Fault Zone from the raw earthquake catalogue and the main shocks catalogue. Our results indicate that inclusion of aftershocks changes the b value and the seismic activity rate m depending on the proportion of aftershocks in a region while it does not significantly effect the value of the maximum regional magnitude since it is related to the maximum observed magnitude. These changes in the earthquake hazard parameters caused the return periods to be over- and underestimated for smaller and larger events, respectively.  相似文献   

2.
The earthquake hazard in Jordan and its vicinity is assessed on the basis of probabilistic methods. For this purpose, an updated earthquake catalog is compiled which covers the period between AD 1–1989. The earthquakes lie between latitudes 27.0°-35.5° N and longitudes 32.0°-39.0° E. Thirteen seismic zones are defined on a regional seismic and tectonic map presented for the area. Point-source and line-source models are used. The seismic hazard parameters, namely, theb-parameter (of the Gutenberg-Richter relation),m 1 (the upper bound magnitude), and 4 (the annual rate of occurrence of earthquakes with local magnitudeM L 4.0) are calculated for each zone. The results of the seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures, i.e. 50 and 100 years. For each model, two seismic hazard maps are derived. In order to determine the importance of the South-eastern Mediterranean zone and the north part of the Red Sea zone from a seismic hazard point of view for Jordan, one seismic hazard map which corresponds to 50 years' economic life for every model, excluding the seismicity of these zones, is derived.  相似文献   

3.
The maximum likelihood estimation of earthquake hazard parameters (maximum regional magnitudem max, activity rate λ, and theb parameter in the Gutenberg-Richter distribution) is extended to the cases of incomplete and uncertain data. The method accepts mixed data containing only large (extreme) events and a variable quality of complete data with different threshold magnitude values. Uncertainty of earthquake magnitude is specified by two values, the lower and upper magnitude limits. It is assumed that such an interval contains the real unknown magnitude. The proposed approach allows the combination of different quality catalog parts, e.g. those where the assignment of magnitude is questionable and those with magnitudes precisely determined. As an illustration of the method, the seismic hazard analysis for western Norway and adjacent sea area (4–8°E, 58–64°N) is presented on the basis of the strongest earthquakes felt during the period 1831–1889 and three complete catalog parts, covering the period 1890–1987.  相似文献   

4.
Earthquake hazard parameters maximum regional magnitude M max and annual activity rate , and the b parameter of the Gutenberg-Richter relation have been evaluated for parts of East Africa. The applied maximum likelihood method permits the combination of both historical and instrumental data available (the catalog used here covers the interval 1880–1979). In addition, the uncertainty involved in magnitude determination and thresholds of completeness were taken into account. The hazard-parameter determination was performed for two study areas corresponding to segments of the eastern and western branches of the East African rift system. The results for these areas show differences that can be partly explained through the characteristics of the data.  相似文献   

5.
The maximum magnitude, the activity rate, and the Gutenberg-Richterb parameter as earthquake hazard parameters, have been evaluated for Sweden. The maximum likelihood method permits the combination of historical and instrumental data. The catalog used consists of 1100 earthquakes in the time interval 1375–1989. The extreme part of the catalog contains only the strongest historical earthquakes, whereas the complete part is divided into several subcatalogs, each assumed complete above a specified threshold magnitude. The uncertainty in magnitude determination was taken into account. For southern Sweden, the calculations giveb-values of 1.04 (0.05) for the whole area south of 60° N and 0.98 (0.06) for a subregion of enhanced seismicity in the Lake Vänern area. For the whole area north of 60° N, theb-value is 1.35 (0.06) and for the seismicity zone along the Gulf of Bothnia 1.26 (0.06). The number of annually expected earthquakes with magnitude equal to or larger than 2.4 [ML(UPP) or MM(UPP)] is 1.8 for the whole southern Sweden, 1.3 for the Lake Vänern region, 3.7 for northern Sweden, and 2.4 for the region along the Gulf of Bothnia. The maximum expected regional magnitude is calculated to 4.9 (0.5) for a time span of 615 years for southern Sweden and the Lake Vänern subregion, and 4.3 (0.5) for a time span of 331 years for northern Sweden and the Gulf of Bothnia subregion. However, several historical earthquakes with magnitude above 5 in nearby areas of Norway indicate that the seismic potential may be higher.  相似文献   

6.
A seismic hazard evaluation for three dams in the Rocky Mountains of northern Colorado is based on a study of the historical seismicity. To model earthquake occurrence as a random process utilizing a maximum likelihood method, the catalog must exhibit random space-time characteristics. This was achieved using a declustering procedure and correction for completeness of recording. On the basis of the resulting a- and b-values, probabilistic epicentral distances for a 2 × 10–5 annual probability were calculated. For a random earthquake of magnitude M L 6.0–6.5, this distance is 15 km. Suggested ground motion parameters were estimated using a probabilistic seismic hazard analysis. Critical peak horizontal accelerations at the dams are 0.22g if median values are assumed and 0.39g if variable attenuation and seismicity rates are taken into account. For structural analysis of the dams, synthetic acceleration time series were calculated to match the empirical response spectra. In addition, existing horizontal strong motion records from two Mammoth Lakes, California earthquakes were selected and scaled to fit the target horizontal acceleration response spectra.  相似文献   

7.
A probabilistic method is used to evaluate the seismichazard of Adassiya dam site on the Yarmouk river in Jordan. A line source model developedby McGuire (1978) is used in this study. An updated earthquake catalogue coveringthe period from 1 A.D. to 1996 A.D. is used for this purpose. This catalogue includesall earthquakes that occurred in Jordan and adjacent areas, more specifically between latitudes27.0°–35.5°N and longitudes 32.0°–39.0°E.Nine distinct seismic sources of potential seismic activitiesare identified. The seismic hazard parameters are determined using the method suggested by Kijko and Sellevoll (1989).The Peak Ground Acceleration (PGA) is selected as a measure of ground motion severity. Esteva (1974) attenuation relationship is used in evaluating PGA values at each dam site. Analysis is carried out for 50%, 90%, and 95% probability that is not being exceeded in a life time of 50, 100, and 200 years.Results of analysis indicate that PGA values at the dam site are as follows:[] Operating Basis Earthquake (OBE) (50% probabilityof non-exceedance for a design life of 100 years – corresponding to a return period of 145 years) is 133.6 cm/sec2.[] An earthquake with 90% probability of non-exceedancefor a design life of 50 years – corresponding to a return period of 475 years is 214.9 cm/sec2.[] Maximum Credible Earthquake (MCE) (Return period of900 years) is 283.0 cm/sec2.Strong motion acceleration time history of these earthquakes are givenbased on strong motion records of the November 1995 Gulf of Aqaba earthquake.Local site effect analysis for Adassiya Dam site using SHAKE program showed no amplification. Normalized site-specific acceleration response spectra for OBE and MCE design earthquakes is also given.  相似文献   

8.
Seismic hazard of Egypt   总被引：1，自引：0，他引：1  
Earthquake hazard parameters such as maximum expected magnitude,M max, annual activity rate,, andb value of the Gutenberg-Richter relation have been evaluated for two regions of Egypt. The applied maximum likelihood method permits the combination of both historical and instrumental data. The catalogue used covers earthquakes with magnitude 3 from the time interval 320–1987. The uncertainties in magnitude estimates and threshold of completeness were taken into account. The hazard parameter determination is performed for two study areas. The first area, Gulf of Suez, has higher seismicity level than the second, all other active zones in Egypt.b-values of 1.2 ± 0.1 and 1.0 ± 0.1 are obtained for the two areas, respectively. The number of annually expected earthquakes with magnitude 3 is much larger in the Gulf of Suez, 39 ± 2 than in the other areas, 6.1 ± 0.5. The maximum expected magnitude is calculated to be 6.5 ± 0.4 for a time span of 209 years for the Gulf of Suez and 6.1 ± 0.3 for a time span of 1667 years for the remaining active areas in Egypt. Respective periods of 10 and 20 years were reported for earthquakes of magnitude 5.0 for the two subareas.  相似文献   

9.
The earthquake hazard parameters and earthquake occurrence probabilities are computed for the different regions of the North Anatolia Fault Zone (NAFZ) using Bayesian method. A homogenous earthquake catalog for M S magnitude which is equal or larger than 4.0 is used for a time period between 1900 and 2015. Only two historical earthquakes (1766, M S = 7. 3 and 1897, M S = 7. 0) are included in Region 2 (Marmara Region) where a large earthquake is expected in the near future since no large earthquake has been observed for the instrumental period. In order to evaluate earthquake hazard parameters for next 5, 10, 20, 50, 100 years, M max (maximum regional magnitude), β value, λ (seismic activity or density) are computed for the different regions of NAFZ. The computed M max values are changed between 7.11 and 7.89. While the highest magnitude value is calculated in the Region 9 related to Tokat-Erzincan, the lowest value in the Region 10 including the eastern of Erzincan. The “quantiles” of “apparent” and “true” magnitudes of future time intervals of 5, 10, 20, 50, and 100 years are calculated for confidence limits of probability levels of 50, 70 and 90 % of the 10 different seismic source regions. The region between Tokat and Erzincan has earthquake hazard level according to the determined parameters. In this region the expected maximum earthquake size is 7.8 with 90 % occurrence probability in next 100 years. While the regional M max value of Marmara Region is computed as 7.61, expected maximum earthquake size is 7.37 with 90 % occurrence probability in next 100 years.  相似文献   

10.
The assessment of seismic hazard parameters is important in the seismically active regions. A straightforward approach is considered for the statistical estimation of the maximum values of earthquake hazard parameters. The Bayesian estimator is suggested and emphasis is given to the evaluation of the maximum possible Mmax (regional) magnitude in a future time interval T. This approach allows the uncertainty of earthquake magnitude to be accounted for. Seismic hazard parameters like the -value which is the slope of the magnitude-frequency law (where, b = loge) and the intensity (rate) of seismic activity and their uncertainties are also estimated. The quantiles of functions of distributions of true and apparent magnitude on a given time interval [0, T] are evaluated, as well. Two main assumptions are adopted for the method:(1) earthquake occurrence is Poissonian and(2) the magnitude-frequency law is of Gutenberg-Richter type with a cutoff maximum value of magnitude. It is needless to say the seismic catalog used must have a large number of events. This requirement leads to the estimation of the parameters referred to some of the most seismically active regions of the world, e.g., Chile, Peru-Equador-South Colombia,Central America and Mexico, which belong to the east part of the circum-Pacific belt.  相似文献   

11.
The assemblage paragonite + quartz is encountered frequently in low- to medium-grade metamorphic rocks. With rising grade of metamorphism they react mutually to yield the condensed assemblage albite + Al2SiO5.The univariant curve pertaining to the equilibrium paragonite + quartz=albite + andalusite + H2O has been located experimentally. The reversed P H 2 O-T data are: 1 kb: 470–490° C 2 kb: 510–530° C 3 kb: 540–560° C 4 kb: 560–580° C 5 kb: 590–600° C The univariant curve pertaining to the equilibrium paragonite + quartz=albite + kyanite + H2O runs through the following P H 2 O-T-intervals: 5 kb: 570–625° C 6 kb: 600–630° C 7 kb: 620–640° C Thermodynamic calculations of S 298 0 , H f,298 0 and G f,298 0 of the phase paragonite from the experimental data presented above and those obtained from the equilibria of the reaction paragonite=albite + corundum + H2O (Chatterjee, 1970), agree within the limits of uncertainty. This prompts the idea that Zen's (1969) suggestion of a possible error of approximately 7 kcal in G f,298 0 of the Al2SiO5 polymorphs may in fact be due to an error of similar magnitude in G f,298 0 of corundum.A best estimate of S 298 0 , H f,298 0 and G f,298 0 of paragonite based on these considerations yield: S 298 0 : 67.61±3.9 cal deg–1 gfw–1 H f,298 0 : –1411.4±2.7 kcal gfw–1 G f,298 0 : –1320.9±4.0 kcal gfw–1 These numbers will be subject to change when better thermochemical data on corundum and albite are available.In medium-grade metamorphic rocks the assemblage paragonite + quartz is commonly found in stable coexistence with such other phases as muscovite, staurolite, andalusite, kyanite, but not with cordierite or sillimanite. However, the assemblage paragonite-sillimanite has been reported to be stable in the absence of quartz. All these petrologic observations can be explained on the basis of the stability data of the phases and phase assemblages concerned.  相似文献   

12.
Spatial variation of seismicity parameters across India and adjoining areas   总被引：2，自引：2，他引：0  
An attempt has been made to quantify the variability in the seismic activity rate across the whole of India and adjoining areas (0–45°N and 60–105°E) using earthquake database compiled from various sources. Both historical and instrumental data were compiled and the complete catalog of Indian earthquakes till 2010 has been prepared. Region-specific earthquake magnitude scaling relations correlating different magnitude scales were achieved to develop a homogenous earthquake catalog for the region in unified moment magnitude scale. The dependent events (75.3%) in the raw catalog have been removed and the effect of aftershocks on the variation of b value has been quantified. The study area was divided into 2,025 grid points (1°×1°) and the spatial variation of the seismicity across the region have been analyzed considering all the events within 300 km radius from each grid point. A significant decrease in seismic b value was seen when declustered catalog was used which illustrates that a larger proportion of dependent events in the earthquake catalog are related to lower magnitude events. A list of 203,448 earthquakes (including aftershocks and foreshocks) occurred in the region covering the period from 250 B.C. to 2010 A.D. with all available details is uploaded in the website .  相似文献   

13.
The Gulf of Aqaba is considered seismically as one of the most active zones of the Dead Sea Transform region. The main shock of the 1995 Gulf of Aqaba earthquake sequence is considered as the largest shock in the (surface wave magnitude Ms?=?7.2) since the sixteenth century. The present study is a trial to detect the probabilistic seismic hazard analysis (PSHA) for Nuweiba site. Data used for this study was a combination of both historical and recent instrumental data. Results of the hazard assessment, expressed as in the worst case scenario, reveal that Nuweiba is exposed to the occurrence of a maximum credible earthquake of magnitude $ m_{{\max }} ~ = ~7.4 \pm 0.31 $ , at hypocentral distance of 15.6?±?10 km. For structure with the return period of 100 years, with a 90% probability of exceedance, the maximum expected earthquake magnitude (ML) is 5.9 in this lifetime. The possibility of the maximum peak ground acceleration at the Nuweiba site is 0.41 g. Results of the hazard assessment can be used as an input data to assess the seismic risk for site of interest.  相似文献   

14.
The diffusion rate of 18O tracer atoms in anorthite (An97Ab03) under anhydrous conditions has been measured using SIMS techniques. The tracer source was 18O2 98.4% gas at 1 bar, in the temperature range 1300° C–850° C. The measured diffusion constants are D 0=1 –0.6 +1 ×10–9 m2s–1 Q=236±8 kJ mol–1 Comparison of these values with published data for 18O diffusion in anorthite under hydrothermal conditions shows that dry oxygen diffusivities are orders of magnitude lower than equivalent wet values at similar temperatures. The effect of these differences on oxygen isotope equilibration during cooling is discussed.  相似文献   

15.
The mineral paragonite, NaAl2[AlSi3O10 (OH)]2, has been synthesized on its own composition starting from a variety of different materials. Indexed powder data and refined cell parameters are given for both the 1M and 2M1 polymorphs obtained. The upper stability limit of paragonite is marked by its breakdown to albite + corundum + vapour. The univariant equilibria pertaining to this reaction have been established by reversing the reaction at six different pressures, the equilibrium curve running through the following intervals: 1 kb: 530°–550° C 2 kb: 555°–575° C 3 kb: 580°–600° C 5kb: 625°–640° C 6 kb: 620°–650° C 7 kb: 650°–670° C.Comparison with the upper stability limit of muscovite (Velde, 1966) shows that paragonite has a notably lower thermal stability thus explaining the field observation that paragonite is absent in many higher grade metamorphic rocks in which muscovite is still stable.The enthalpy and entropy of the paragonite breakdown reaction have been estimated. Since intermediate albites of varying structural states are in equilibrium with paragonite, corundum and H2O along the univariant equilibrium curve, two sets of data pertaining to the entropy of paragonite (S 298 0 ) as well as the enthalpy ( H f,298 0 ) and Gibbs free energy ( G f,298 0 ) of its formation were computed, assuming (1) high albite and (2) low albite as the equilibrium phase. The values are: (1) (2) S 298 0 67.8±3.9 cal deg–1 gfw–1 63.7±3.9 cal deg–1 gfw–1 H f,298 0 –1417.9±2.7 kcal gfw–1 –1420.2±2.6 kcal gfw–1 G f,298 0 –1327.4±4.0 kcal gfw–1 –1328.5±4.0 kcal gfw–1.Adapted from a part of the author's Habilitationsschrift accepted by the Ruhr University, Bochum (Chatterjee, 1968).  相似文献   

16.
We conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for Turkey and the adjacent areas, applying the maximum likelihood method. The procedure allows for the use of either historical or instrumental data, or even a combination of the two. By using this method, we can estimate the earthquake hazard parameters, which include the maximum regional magnitude Mˆmax, the activity rate of seismic events and the well-known bˆ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. These three parameters are determined simultaneously using an iterative scheme. The uncertainty in the determination of the magnitudes was also taken into consideration. The return periods (RP) of earthquakes with a magnitude M ≥ m are also evaluated. The whole examined area is divided into 24 seismic regions based on their seismotectonic regime. The homogeneity of the magnitudes is an essential factor in such studies. In order to achieve homogeneity of the magnitudes, formulas that convert any magnitude to an MS-surface scale are developed. New completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions. Each of the obtained parameters is distributed into its respective seismic region, allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map. The earthquake hazard level is also calculated as a function of the form Θ = (Mˆmax,RP6.0), and a relative hazard scale (defined as the index K) is defined for each seismic region. The investigated regions are then classified into five groups using these parameters. This classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity. An attempt is then made to relate these values to the local tectonics.  相似文献   

17.
This paper presents a seismic hazard evaluation and develops an earthquake catalogue for the Constantine region over the period from 1357 to 2014. The study contributes to the improvement of seismic risk management by evaluating the seismic hazards in Northeast Algeria. A regional seismicity analysis was conducted based on reliable earthquake data obtained from various agencies (CRAAG, IGN, USGS and ISC). All magnitudes (M l, m b) and intensities (I 0, I MM, I MSK and I EMS) were converted to M s magnitudes using the appropriate relationships. Earthquake hazard maps were created for the Constantine region. These maps were estimated in terms of spectral acceleration (SA) at periods of 0.1, 0.2, 0.5, 0.7, 0.9, 1.0, 1.5 and 2.0 s. Five seismogenic zones are proposed. This new method differs from the conventional method because it incorporates earthquake magnitude uncertainty and mixed datasets containing large historical events and recent data. The method can be used to estimate the b value of the Gutenberg-Richter relationship, annual activity rate λ(M) of an event and maximum possible magnitude M max using incomplete and heterogeneous data files. In addition, an earthquake is considered a Poisson with an annual activity rate λ and with a doubly truncated exponential earthquake magnitude distribution. Map of seismic hazard and an earthquake catalogue, graphs and maps were created using geographic information systems (GIS), the Z-map code version 6 and Crisis software 2012.  相似文献   

18.
Speidel  D. H.  Mattson  P. H. 《Natural Hazards》1997,16(2-3):165-179
The use of b-values derived from the Gutenberg–Richter relationship as a phenomenological base for developing probabilistic seismic hazard analyses (PSHA) has been questioned for years. The relationship is still used because political demands require something for PSHA, one variable is easy to deal with, and no persuasive alternative has come forward. Using cumulative distribution probability plots, it can be shown that seismic magnitude-frequency data can be well described as one or more populations, each of which is normally distributed with respect to magnitude. This holds true for large earthquakes when sorted by mechanism, for earthquakes >400 km deep, for the general USGS NEIC catalog, for the Harvard CMT catalog, for the CERI catalog of the New Madrid Zone, and for a Scandinavian catalog. In all instances, multiple normal populations provide a better fit to the data than does the Gutenberg–Richter relationship. Use of these multiple populations in PSHA emphasizes that the scientifically sound limits of magnitude projection are within the 4 limit of the largest populations. Such graphs may make it easier to resist political requirement to extrapolate into scientifically unsound regions.  相似文献   

19.
The 19 November 1923 earthquake in the Aran Valley (Central Pyrenees), with observed maximum intensityI max = VIII (MSK), has been studied through the compiling and reviewing of macroseismic information and collecting and processing early seismograms. Analysis of macroseismic data gives a focal depth ofh = 5 km and an anelastic attenuation coefficient 10–3 km–1. Analysis of early instrumental records allows the computation of estimate of magnitude (M L = 5.6) and seismic moment (M o = 1.1 × 1017 N × m) which are consistent with the values ofI o andh obtained from macroseismic data.  相似文献   

20.
The Larderello geothermal field is generally accepted to have been produced by a granite intrusion at 4–9 km depth. Hydrothermal parageneses and fluid inclusions always formed at temperatures greater than or equal to the current ones, which implies that the field has always undergone a roughly monotonic cooling history (fluctuations < 40 K) since intrusion of the granite at 4 Ma. The heat required to maintain the thermal anomaly over such a long period is supplied by a seismically anomalous body of 32000 km3 rooted in the mantle. Borehole minerals from Larderello are thus a unique well-calibrated natural example of thermally induced Ar and Sr loss under geological conditions and time spans. The observations (biotites retain Ar above 450°C) agree well with other, albeit less precise, geological determinations, but contrast with laboratory determinations of diffusivity from the literature. We therefore performed a hydrothermal experiment on two Larderello biotites and derived a diffusivity D Lab(370°C)=5.3·10-18 cm2s-1, in agreement with published estimates of diffusivity in annite. From D Lab and the rejuvenation of the K/Ar ages we calculate maximum survival times at the present in-hole temperatures. They trend smoothly over almost two orders of magnitude from 352 ka to 5.3 ka, anticorrelating with depth: laboratory diffusivities are inconsistent not only with geological facts, but also among themselves. From the geologically constrained lifetime of the thermal anomaly we derive a diffusivity D G(370°C)=3.81·1021 cm2s-1, 3±1 orders of magnitude lower than D Lab. The cause of these discrepancies must be sought among various laboratory artefacts: overstepping of a critical temperature T *; enhanced diffusivities in wet experiments; presence of fast pathway (dislocation and pipe) diffusion, and of dissolution/reprecipitation reactions, which we imaged by scanning electron microscopy. These phenomena are minor in geological settings: in the absence of mineral transformation reactions, complete or near-complete resetting is achieved only by volume diffusion. Therefore, laboratory determinations will necessarily result in apparent diffusivities that are too high compared to those actually effecting the resetting of natural geochronometers.This word is dedicated to the memory of Aldo Valori (1958–1991)  相似文献   

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