首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing regional seismic hazard maps based on morphostructural analysis, pattern recognition, and the Unified Scaling Law for Earthquakes (USLE), which generalizes the Gutenberg-Richter relationship making use of naturally fractal distribution of earthquake sources of different size in a seismic region. The USLE stands for an empirical relationship log10N(M, L)?=?A?+?B·(5 – M)?+?C·log10L, where N(M, L) is the expected annual number of earthquakes of a certain magnitude M within a seismically prone area of linear dimension L. We use parameters A, B, and C of USLE to estimate, first, the expected maximum magnitude in a time interval at seismically prone nodes of the morphostructural scheme of the region under study, then map the corresponding expected ground shaking parameters (e.g., peak ground acceleration, PGA, or macro-seismic intensity). After a rigorous verification against the available seismic evidences in the past (usually, the observed instrumental PGA or the historically reported macro-seismic intensity), such a seismic hazard map is used to generate maps of specific earthquake risks for population, cities, and infrastructures (e.g., those based on census of population, buildings inventory). The methodology of seismic hazard and risk assessment is illustrated by application to the territory of Greater Caucasus and Crimea.  相似文献   

2.
One of the crucial components in seismic hazard analysis is the estimation of the maximum earthquake magnitude and associated uncertainty. In the present study, the uncertainty related to the maximum expected magnitude μ is determined in terms of confidence intervals for an imposed level of confidence. Previous work by Salamat et al. (Pure Appl Geophys 174:763-777, 2017) shows the divergence of the confidence interval of the maximum possible magnitude mmax for high levels of confidence in six seismotectonic zones of Iran. In this work, the maximum expected earthquake magnitude μ is calculated in a predefined finite time interval and imposed level of confidence. For this, we use a conceptual model based on a doubly truncated Gutenberg-Richter law for magnitudes with constant b-value and calculate the posterior distribution of μ for the time interval Tf in future. We assume a stationary Poisson process in time and a Gutenberg-Richter relation for magnitudes. The upper bound of the magnitude confidence interval is calculated for different time intervals of 30, 50, and 100 years and imposed levels of confidence α?=?0.5, 0.1, 0.05, and 0.01. The posterior distribution of waiting times Tf to the next earthquake with a given magnitude equal to 6.5, 7.0, and 7.5 are calculated in each zone. In order to find the influence of declustering, we use the original and declustered version of the catalog. The earthquake catalog of the territory of Iran and surroundings are subdivided into six seismotectonic zones Alborz, Azerbaijan, Central Iran, Zagros, Kopet Dagh, and Makran. We assume the maximum possible magnitude mmax?=?8.5 and calculate the upper bound of the confidence interval of μ in each zone. The results indicate that for short time intervals equal to 30 and 50 years and imposed levels of confidence 1???α?=?0.95 and 0.90, the probability distribution of μ is around μ?=?7.16???8.23 in all seismic zones.  相似文献   

3.
In the present study, the level of the largest earthquake hazard is assessed in 28 seismic zones of the NW Himalaya and its vicinity, which is a highly seismically active region of the world. Gumbel’s third asymptotic distribution (hereafter as GIII) is adopted for the evaluation of the largest earthquake magnitudes in these seismic zones. Instead of taking in account any type of Mmax, in the present study we consider the ω value which is the largest earthquake magnitude that a region can experience according to the GIII statistics. A function of the form Θ(ω, RP6.0) is providing in this way a relatively largest earthquake hazard scale defined by the letter K (K index). The return periods for the ω values (earthquake magnitudes) 6 or larger (RP6.0) are also calculated. According to this index, the investigated seismic zones are classified into five groups and it is shown that seismic zones 3 (Quetta of Pakistan), 11 (Hindukush), 15 (northern Pamirs), and 23 (Kangra, Himachal Pradesh of India) correspond to a “very high” K index which is 6.  相似文献   

4.
Statistical tests have been used to adjust the Zemmouri seismic data using a distribution function. The Pareto law has been used and the probabilities of various expected earthquakes were computed. A mathematical expression giving the quantiles was established. The extreme values limiting law confirmed the accuracy of the adjustment method. Using the moment magnitude scale, a probabilistic model was made to predict the occurrences of strong earthquakes. The seismic structure has been characterized by the slope of the recurrence plot γ, fractal dimension D, concentration parameter Ksr, Hurst exponents Hr and Ht. The values of D, γ, Ksr, Hr, and Ht diminished many months before the principal seismic shock (M = 6.9) of the studied seismoactive zone has occurred. Three stages of the deformation of the geophysical medium are manifested in the variation of the coefficient G% of the clustering of minor seismic events.  相似文献   

5.
We present the seismic source zoning of the tectonically active Greater Kashmir territory of the Northwestern Himalaya and seismicity analysis (Gutenberg-Richter parameters) and maximum credible earthquake (m max) estimation of each zone. The earthquake catalogue used in the analysis is an extensive one compiled from various sources which spans from 1907 to 2012. Five seismogenic zones were delineated, viz. Hazara-Kashmir Syntaxis, Karakorum Seismic Zone, Kohistan Seismic Zone, Nanga Parbat Syntaxis, and SE-Kashmir Seismic Zone. Then, the seismicity analysis and maximum credible earthquake estimation were carried out for each zone. The low b value (<1.0) indicates a higher stress regime in all the zones except Nanga Parbat Syntaxis Seismic Zone and SE-Kashmir Seismic Zone. The m max was estimated following three different methodologies, the fault parameter approach, convergence rates using geodetic measurements, and the probabilistic approach using the earthquake catalogue and is estimated to be M w 7.7, M w 8.5, and M w 8.1, respectively. The maximum credible earthquake (m max) estimated for each zone shows that Hazara Kashmir Syntaxis Seismic Zone has the highest m max of M w 8.1 (±0.36), which is espoused by the historical 1555 Kashmir earthquake of M w 7.6 as well as the recent 8 October 2005 Kashmir earthquake of M w 7.6. The variation in the estimated m max by the above discussed methodologies is obvious, as the definition and interpretation of the m max change with the method. Interestingly, historical archives (～900 years) do not speak of a great earthquake in this region, which is attributed to the complex and unique tectonic and geologic setup of the Kashmir Himalaya. The convergence is this part of the Himalaya is distributed not only along the main boundary faults but also along the various active out-of-sequence faults as compared to the Central Himalaya, where it is mainly adjusted along the main boundary fault.  相似文献   

6.
The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m b and M d to M s or M w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes.  相似文献   

7.
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   

8.
In this study, strong ground motion record(SGMR) selection based on Eta(η) as a spectral shape indicator has been investigated as applied to steel braced frame structures. A probabilistic seismic hazard disaggregation analysis for the definition of the target Epsilon(ε) and the target Eta(η) values at different hazard levels is presented, taking into account appropriately selected SGMR's. Fragility curves are developed for different limit states corresponding to three representative models of typical steel braced frames having significant irregularities in plan, by means of a weighted damage index. The results show that spectral shape indicators have an important effect on the predicted median structural capacities, and also that the parameter η is a more robust predictor of damage than searching for records with appropriate ε values.  相似文献   

9.
The Sakarya prefecture is an interesting area with various seismicity types. This activity comes from earthquakes occurring at the North Anatolian Fault Zone and from a few quarry blast areas in the region. These quarry blast recordings produce errors in the determination of active faults and mapping of the microearthquake activity. Therefore, to recognize the tectonic activity in the region, we need to be able to discriminate between earthquakes and quarry blasts in the catalogues. In this study, a statistical analysis method (linear discriminant function) has been applied to classify seismic events occurring in the Sakarya region. We used 110 seismic events that were recorded by Sakarya University Seismic Station between 2012 and 2014. Time and frequency variant parameters, maximum S wave and maximum P wave amplitude ratio (S/P), the spectral ratio (Sr), maximum frequency (fmax), and total signal duration of the waveform were used for discrimination analyses. The maximum frequency (fmax) versus time duration of the seismic signal gives a higher classification percentage (94%) than the other discriminants. At the end of this study, 41 out of 110 events (44%) are determined as quarry blasts, and 62 (56%) are considered as earthquakes.  相似文献   

10.
We performed a tectonophysical analysis of earthquake frequency–size relationship types for large Central Asian earthquakes in the regions of dynamical influence due to major earthquake-generating faults based on data for the last 100 years. We identified four types of frequency–size curves, depending on the presence/absence of characteristic earthquakes and the presence or absence of a downward bend in the tail of the curve. This classification by the shape of the tail in frequency–size relationships correlates well with the values of the maximum observed magnitude. Thus, faults of the first type (there are characteristic earthquakes, but no downward bend) with Mmax ≥ 8.0 are classified as posing the highest seismic hazard; faults with characteristic earthquakes and a bend, and with Mmax = 7.5–7.9, are treated as rather hazardous; faults of the third type with Mmax = 7.1–7.5 are treated as posing potential hazard; and lastly, faults with a bend, without characteristic earthquakes, and with a typical magnitude Mmax ≤ 7.0, are classified as involving little hazard. The tail types in frequency–size curves are interpreted using the model of a nonlinear multiplicative cascade. The model can be used to treat different tail types as corresponding to the occurrence/nonoccurrence of nonlinear positive and negative feedback in earthquake rupture zones, with this feedback being responsible for the occurrence of earthquakes with different magnitudes. This interpretation and clustering of earthquake-generating faults by the behavior the tail of the relevant frequency–size plot shows raises the question about the physical mechanisms that underlie this behavior. We think that the occurrence of great earthquakes is related to a decrease in effective strength (viscosity) in the interblock space of faults at a scale appropriate to the rupture zone size.  相似文献   

11.
During the ruptures of an earthquake,the strain energy.△E,.will be transferred into,at least,three parts,i.e..the seismic radiation energy(E_s),fracture energy(E_g),and frictional energy(E_f),that is,△E = E_s + E_g + E_f.Friction,which is represented by a velocity- and state-dependent friction law by some researchers,controls the three parts.One of the main parameters of the law is the characteristic slip displacement.D_c.It is significant and necessary to evaluate the reliable value of D_c from observed and inverted seismic data.Since D_c controls the radiation efficiency.η_R = E_s/(E_s+ E_g),the value of η_r is a good constraint of estimating D_c.Integrating observed data and inverted results of source parameters from recorded seismograms.the values of E_s and E_g of an earthquake can be measured,thus leading to the value of η_R.The constraint used to estimate the reliable value of D_c will be described in this work.An example of estimates of D_c.based on the observed and inverted values of source parameters of the September 20,1999 M_S 7.6 Chi-Chi(Ji-Ji).Taiwan region,earthquake will be presented.  相似文献   

12.
The 2017 Guptkashi earthquake occurred in a segment of the Himalayan arc with high potential for a strong earthquake in the near future. In this context, a careful analysis of the earthquake is important as it may shed light on source and ground motion characteristics during future earthquakes. Using the earthquake recording on a single broadband strong-motion seismograph installed at the epicenter, we estimate the earthquake’s location (30.546° N, 79.063° E), depth (H?=?19 km), the seismic moment (M0?=?1.12×1017 Nm, M w 5.3), the focal mechanism (φ?=?280°, δ?=?14°, λ?=?84°), the source radius (a?=?1.3 km), and the static stress drop (Δσ s ~22 MPa). The event occurred just above the Main Himalayan Thrust. S-wave spectra of the earthquake at hard sites in the arc are well approximated (assuming ω?2 source model) by attenuation parameters Q(f)?=?500f0.9, κ?=?0.04 s, and fmax?=?infinite, and a stress drop of Δσ?=?70 MPa. Observed and computed peak ground motions, using stochastic method along with parameters inferred from spectral analysis, agree well with each other. These attenuation parameters are also reasonable for the observed spectra and/or peak ground motion parameters in the arc at distances ≤?200 km during five other earthquakes in the region (4.6?≤?M w ?≤?6.9). The estimated stress drop of the six events ranges from 20 to 120 MPa. Our analysis suggests that attenuation parameters given above may be used for ground motion estimation at hard sites in the Himalayan arc via the stochastic method.  相似文献   

13.
Seismic intensity measures (IMs) perform a pivotal role in probabilistic seismic demand modeling. Many studies investigated appropriate IMs for structures without considering soil liquefaction potential. In particular, optimal IMs for probabilistic seismic demand modeling of bridges in liquefied and laterally spreading ground are not comprehensively studied. In this paper, a coupled-bridge-soil-foundation model is adopted to perform an in-depth investigation of optimal IMs among 26 IMs found in the literature. Uncertainties in structural and geotechnical material properties and geometric parameters of bridges are considered in the model to produce comprehensive scenarios. Metrics such as efficiency, practicality, proficiency, sufficiency and hazard computability are assessed for different demand parameters. Moreover, an information theory based approach is adopted to evaluate the relative sufficiency among the studied IMs. Results indicate the superiority of velocity-related IMs compared to acceleration, displacement and time-related ones. In particular, Housner spectrum intensity (HI), spectral acceleration at 2.0 s (S a-20), peak ground velocity (PGV), cumulative absolute velocity (CAV) and its modified version (CAV 5) are the optimal IMs. Conversely, Arias intensity (I a ) and shaking intensity rate (SIR) which are measures often used in liquefaction evaluation or related structural demand assessment demonstrate very low correlations with the demand parameters. Besides, the geometric parameters do not evidently affect the choice of optimal IMs. In addition, the information theory based sufficiency ranking of IMs shows an identical result to that with the correlation measure based on coefficient of determination (R 2). This means that R 2 can be used to preliminarily assess the relative sufficiency of IMs.  相似文献   

14.
The complex seismotectonic studies of the pleistoseist area of the Ilin-Tas earthquake (Ms = 6.9), one of the strongest seismic events ever recorded by the regional seismic network in northeastern Russia, are carried out. The structural tectonic position, morphotectonic features of present-day topography, active faults, and types of Cenozoic deformations of the epicentral zone are analyzed. The data of the instrumental observations are summarized, and the manifestations of the strong seismic events in the Yana–Indigirka segment of the Cherskii seismotectonic zone are considered. The explanation is suggested for the dynamical tectonic setting responsible for the Andrei-Tas seismic maximum. This setting is created by the influence of the Kolyma–Omolon indenter, which intrudes into the Cherskii seismotectonic zone from the region of the North American lithospheric plate and forms the main seismogenic structures of the Yana–Indigirka segment in the frontal zone (the Ilin-Tas anticlinorium). The highest seismic potential is noted in the Andrei- Tas block—the focus of the main tectonic impacts from the Kolyma–Omolon superterrane. The general trend of this block coincides with the orientation of the major axis of isoseismal ellipses (azimuth 50°–85°), which were determined from the observations of macroseismic effects on the ground after the Uyandina (Ms = 5.6), Andrei-Tas (Ms = 6.1), and Ilin-Tas (Ms = 6.9) earthquakes.  相似文献   

15.
We analyzed the most relevant seismic sequences that occurred from 1977 to 2007 in the Friuli-Venezia Giulia region (northeastern Italy) and western Slovenia. The eight aftershock sequences were triggered by low- to moderate-magnitude earthquakes with mainshock duration magnitude ranging from 3.7 to 5.6. The b-value of the Gutenberg–Richter law varies from 0.8 to 1.1. The modified Omori’s modeling of the sequences evidences values of the p exponent ranging from 0.8 to 1.0. Using the Reasenberg and Jones (Science 243:1173–1176, 1989; Science 265:1251–1252, 1994) approach, we computed the probabilistic estimate of the aftershock rates and the largest aftershock in given time intervals. The difference in magnitude between the mainshock and the largest aftershock is calculated according to the modified Båth law and using an approach that considers the partitioning of the radiated seismic energy between mainshock and aftershocks. The partitioning of the radiated seismic energy appears to play a significant role in the evolution of the sequences. We define the parameter R ES as the ratio between the radiated seismic energy of the mainshock and the summation of the seismic energy radiated by the aftershocks. The difference in magnitude between the mainshock and the largest aftershock, calculated with the parameter R ES, agrees well with the observed difference. In most sequences, the parameter R ES decreases very quickly until the occurrence of the largest aftershock and then becomes constant. By analyzing the values of R ES during the early hours following the mainshock, we found that the R ES values after 24 h are well related to the final ones, calculated on the whole sequence, and to the differences in magnitude between the mainshock and the largest aftershock.  相似文献   

16.
In this paper, we calculated the seismic pattern of instrumental recorded small and moderate earthquakes near the epicenter of the 1303 Hongtong M=8 earthquake, Shanxi Province. According to the spatial distribution of small and moderate earthquakes, 6 seismic dense zones are delineated. Temporal distribution of M L≥2 earthquakes since 1970 in each seismic dense zone has been analyzed. Based on temporal distribution characteristics and historical earthquake activity, three types of seismicities are proposed. The relationship between seismic types and crustal medium is analyzed. The mechanism of three types is discussed. Finity of strong earthquake recurrence is proposed. Seismic hazard in mid-long term and diversity of earthquake disaster in Shanxi seismic belt are discussed.  相似文献   

17.
We have analyzed the behavior of the F2 layer parameters during nighttime periods of enhanced electron concentration by the results of vertical sounding of the ionosphere carried out with five-minute periodicity in Almaty (76°55′ E, 43°15′ N) in 2001–2012. The results are obtained within the frameworks of the unified concept of different types of ionospheric plasma disturbances manifested as variations in the height and half-thickness of the layer accompanied by an increase and decrease of N m F2 at the moments of maximum compression and expansion of the layer. A good correlation is found between height h Am , which corresponds to the maximum increase, and layer peak height h m F, while h Am is always less than h m F. The difference between h Am and h m F linearly increases with increasing h m F. Whereas the difference is ~38 km for h m F = 280 km, it is ~54 km for h m F = 380 km. Additionally, the correlation is good between the increase in the electron concentration in the layer maximum ΔN m and the maximum enhancement at the fixed height ΔN; the electron concentration enhancement in the layer maximum is about two to three times lower than its maximum enhancement at the fixed height.  相似文献   

18.
An important task in seismic hazard assessment is estimation of the intensity and frequency of extremely strong earthquake effects, in particular, peak ground velocities (PGV). Earlier, a method was proposed to evaluate PGV values based on the magnitude of displacements of rock blocks (Rodkin et al., 2012). In this study, this method is used to analyze field data on the source zones of the August 19, 1992, MS = 7.3 Susamyr earthquake and the January 3, 1911, Mw = 7.9 Kemin earthquake, and estimate maximum ground shaking at the upper construction site of the Upper Naryn series of hydropower plants, Kyrgyz Republic. It is shown that the resulting estimates are consistent with data obtained through other techniques. Therefore, the new approach can be recommended to estimate earthquake effects.  相似文献   

19.
Different values have been assigned to the ratio of the defl ection amplifi cation factor(Cd) to the response modifi cation factor(R) for a specifi ed force-resisting system in the seismic design provisions while the same application is defi ned for it. An analytical study of the seismic responses of several reinforced concrete frames subjected to a suite of earthquake records performed in this research indicate that the stories’ overstrength and stiffness distribution along the structural height can affect local defl ections more than global ones. Therefore, the Cd/R ratio is calculated based on the ratio of both maximum inelastic to maximum elastic displacements and interstory drifts. Due to damage concentration in some specifi c stories, the defl ection amplifi cation factor calculated based on inelastic interstory drifts was larger than that of the inelastic displacements. Consequently, a minimum value of 1.0 is recommended for the Cd/R ratio in order to estimate maximum inelastic drifts. The ratio of inelastic to elastic displacement was generally found to increase slightly along the structural height for the studied RC models. In addition, it was detected that the story damage indices of the studied RC frames decrease when the inverted value of inelastic interstory drift ratios are increased through a(negative) power form.  相似文献   

20.
A multi-event and multi-station inverse method is presented in the paper to simultaneously estimate the seismic moments (M 0) and source corner frequencies (f c) of several Jiashi (Xinjiang, China) earthquakes, as well as the apparent Lg Q models for the paths from Jiashi to eight seismic stations (WMQ, AAK, TLG, MAKZ, KUR, VOS, ZRN and CHK) in Central Asia. The resultant seismic moments correlate well with the M 0 values obtained by Harvard University using the centroid moment tensor (CMT) inversion and the surface-wave magnitudes as well. After the correction by a typical value of average radiation coefficient for regional SV waves, the M 0 values from Lg spectral inversion are still close to the corresponding values obtained from CMT inversion. The obtained apparent Q 0Lg values (Lg Q at 1 Hz) are consistent with the tectonic features of corresponding propagation paths. The Q 0Lg values are 351±87, 349±86 and 300±27 for the paths from Jiashi to AAK, TLG and MAKZ, respectively. They are smaller than Q 0Lg values for the paths to KUR, VOS, ZRN and CHK, which are 553±72, 569±58, 550±57 and 603±65, respectively. These results agree with the condition that the paths to AAK, TLG and MAKZ mainly propagate through the mountainous Tianshan area where relatively strong seismic activities and large variations of topography are exhibited, while the paths to KUR, VOS, ZRN and CHK mainly propagate through the stable area of Kazak platform. The Q 0Lg value for the path to WMQ is 462±56. This is also in agreement with the condition that the path to WMQ is basically along the border area between Tianshan Mountain and Tarim Basin, and along this path the variations of topography and crustal thickness are moderate in comparison with that along the path to MAKZ.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号