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1.
The present study aims at understanding the seismotectonic province of the Shillong Plateau (SP) by identifying the potential seismic source zones within a radius of 500 km from the centre of the SP. From existing literature and earthquake (EQ) data, the seismotectonic region is found to vary in terms of seismicity, tectonic features, geology, thickness of overburden, rupture characteristics and rate of movement. Thus, entire 500-km-radius seismotectonic region is divided into four seismic source zones: namely (1) the Shillong Plateau–Assam Valley Zone (SP-AVZ), (2) the Indo-Burma Ranges Zone (IBRZ), (3) the Bengal Basin Zone (BBZ) and (4) the Eastern Himalaya Zone (EHZ). EQ catalogues for each source zone is analysed for completeness of magnitude and time. Seismic parameter b estimated using a maximum likelihood method is found to be 0.91 ± 0.03, 0.94 ± 0.02, 0.80 ± 0.03 and 0.89 ± 0.03 for the SP-AVZ, IBRZ, BBZ and EHZ, respectively. In addition, the maximum likelihood method is used to estimate the mean annual activity rate, maximum possible magnitude (m max), return period and probability of exceedance for the four zones. The b values estimated suggest that the BBZ is seismically more active; however, the rate of occurrence of EQs is highest in the IBRZ. Findings from this study are an indication of the relative contribution from each of the four seismic source zones towards a seismic hazard of the SP.  相似文献   

2.
—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   

3.
—?The procedure developed by Kijko and Sellevoll (1989, 1992) and Kijko and Graham (1998, 1999) is used to estimate seismic hazard parameters in north Algeria. The area-specific seismic hazard parameters that were calculated consist of the b value of the Gutenberg–Richter frequency–magnitude relation, the activity rate λ(M) for events above the magnitude M, and the maximum regional magnitude M max. These parameters were calculated for each of the six seismogenic zones of north Algeria. The site-specific seismic hazard was calculated in terms of the maximum possible PGA at hypothetical engineering structures (HES), situated in each of the six seismogenic zones with coordinates corresponding with those of the six most industrial and populated cities in Algeria.  相似文献   

4.
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   

5.
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   

6.
In order to obtain a uniform magnitude catalogue, surface-wave magnitudes Ms and broad-band body-wave magnitudes mB have been determined for large shallow earthquakes from 1904 to 1980. In making the catalogue homogeneous, the author consistently adheres to the original definitions of Ms and mB given by Gutenberg (1945) and Gutenberg and Richter (1956). The determinations of Ms and mB are all based on the amplitude and period data listed in Gutenberg and Richter's unpublished notes, bulletins from stations worldwide, and other basic information. mB is measured on broad-band instruments in periods of ～8 s. Consistency of the magnitude determinations from these different sources is carefully checked in detail. More than 900 shallow shocks of magnitude 7 and over are catalogued. The meaning of the magnitude scales in various catalogues is examined in terms of Ms and mB. Most of the magnitudes listed by Gutenberg and Richter (1954) in their “Seismicity of the Earth” are basically Ms for large shocks shallower than 40 km, but are basically mB for large shocks at depths of 40–60 km. The surface-wave magnitudes given by “Earthquake Data Reports” are higher than Ms by 0.2 unit whether the combined horizontal amplitude or the vertical amplitude is used. mB and the currently used 1 s body-wave magnitude are measured at different periods and should not be directly compared.  相似文献   

7.
Calibration of magnitude scales for earthquakes of the Mediterranean   总被引：1，自引：1，他引：0  
In order to provide the tools for uniform size determination for Mediterranean earthquakes over the last 50-year period of instrumental seismology, we have regressed the magnitude determinations for 220 earthquakes of the European-Mediterranean region over the 1977–1991 period, reported by three international centres, 11 national and regional networks and 101 individual stations and observatories, using seismic moments from the Harvard CMTs. We calibrate M(M0) regression curves for the magnitude scales commonly used for Mediterranean earthquakes (ML, MWA, mb, MS, MLH, MLV, MD, M); we also calibrate static corrections or specific regressions for individual observatories and we verify the reliability of the reports of different organizations and observatories. Our analysis shows that the teleseismic magnitudes (mb, MS) computed by international centers (ISC, NEIC) provide good measures of earthquake size, with low standard deviations (0.17–0.23), allowing one to regress stable regional calibrations with respect to the seismic moment and to correct systematic biases such as the hypocentral depth for MS and the radiation pattern for mb; while mb is commonly reputed to be an inadequate measure of earthquake size, we find that the ISC mb is still today the most precise measure to use to regress MW and M0 for earthquakes of the European-Mediterranean region; few individual observatories report teleseismic magnitudes requiring specific dynamic calibrations (BJI, MOS). Regional surface-wave magnitudes (MLV, MLH) reported in Eastern Europe generally provide reliable measures of earthquake size, with standard deviations often in the 0.25–0.35 range; the introduction of a small (±0.1–0.2) static station correction is sometimes required. While the Richter magnitude ML is the measure of earthquake size most commonly reported in the press whenever an earthquake strikes, we find that ML has not been computed in the European-Mediterranean in the last 15 years; the reported local magnitudes MWA and ML do not conform to the Richter formula and are of poor quality and little use, with few exceptions requiring ad hoc calibrations similar to the MS regression (EMSC, ATH). The duration magnitude MD used by most seismic networks confirms that its use requires accurate station calibrations and should be restricted only to events with low seismic moments.  相似文献   

8.
Maximum earthquake size varies considerably amongst the subduction zones. This has been interpreted as a variation in the seismic coupling, which is presumably related to the mechanical conditions of the fault zone. The rupture process of a great earthquake indicates the distribution of strong (asperities) and weak regions of the fault. The rupture process of three great earthquakes (1963 Kurile Islands, MW = 8.5; 1965 Rat Islands, MW = 8.7; 1964 Alaska, MW = 9.2) are studied by using WWSSN stations in the core shadow zone. Diffraction around the core attenuates the P-wave amplitudes such that on-scale long-period P-waves are recorded. There are striking differences between the seismograms of the great earthquakes; the Alaskan earthquake has the largest amplitude and a very long-period nature, while the Kurile Islands earthquake appears to be a sequence of magnitude 7.5 events.The source time functions are deconvolved from the observed records. The Kurile Islands rupture process is characterized by the breaking of asperities with a length scale of 40–60 km, and for the Alaskan earthquake the dominant length scale in the epicentral region is 140–200 km. The variation of length scale and MW suggests that larger asperities cause larger earthquakes. The source time function of the 1979 Colombia earthquake (MW = 8.3) is also deconvolved. This earthquake is characterized by a single asperity of length scale 100–120 km, which is consistent with the above pattern, as the Colombia subduction zone was previously ruptured by a great (MW = 8.8) earthquake in 1906.The main result is that maximum earthquake size is related to the asperity distribution on the fault. The subduction zones with the largest earthquakes have very large asperities (e.g. the Alaskan earthquake), while the zones with the smaller great earthquakes (e.g. Kurile Islands) have smaller scattered asperities.  相似文献   

9.
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   

10.
Persian territory, which is dividable into major seismotectonic provinces, always suffers from damages of moderate and large earthquakes from ancient era to modern time. Therefore, temporal prediction of earthquake occurrence in this kind of area is an important topic. For this purpose, 628 moderate-large (5.5 ≤MS≤ 8.2) earthquakes occurred in Persia during the period from 400 B.C. to 2015 C.E. were used. Considering the magnitudes of events preceding main shocks and the annual seismic moment release in seismic source areas in the provinces, we calibrated equations predicting inter-event time of occurrence of moderate and large earthquakes (MW>5.5) in Iran. In each source area, inter-event times between moderate and large shocks with magnitudes equal to or larger than a certain cut-off magnitude (MW5.5) were calculated. The inter-event times between the earthquakes were used to compute the relationships using multiple regression technique. Calculated relationships express the basic idea of the time predictable model predicting the occurrence time of the future main shock in a certain seismogen area. However, despite of unavoidable scatter in observations and uncertainties in the results, occurrence times of main shocks during the next years and decades in some source areas in Iran were determined.  相似文献   

11.
The Canterbury earthquake sequence beginning with the 2010 M W 7.2 Darfield earthquake is one of the most notable and well-recorded crustal earthquake sequences in a low-strain-rate region worldwide and as such provides a unique opportunity to better understand earthquake source physics and ground motion generation in such a tectonic setting. Ground motions during this sequence ranged up to extreme values of 2.2 g, recorded during the February 2011 M W 6.2 event beneath the city of Christchurch. A better understanding of the seismic source signature of this sequence, in particular the stress release and its scaling with earthquake size, is crucial for future ground motion prediction and hazard assessment in Canterbury, but also of high interest for other low-to-moderate seismicity regions where high-quality records of large earthquakes are lacking. Here we present a source parameter study of more than 200 events of the Canterbury sequence, covering the magnitude range M W 3–7.2. Source spectra were derived using a generalized spectral inversion technique and found to be well characterized by the ω ?2 source model. We find that stress drops range between 1 and 20 MPa with a median value of 5 MPa, which is a factor of 5 larger than the median stress drop previously estimated with the same method for crustal earthquakes in much more seismically active Japan. Stress drop scaling with earthquake size is nearly self-similar, and we identify lateral variations throughout Canterbury, in particular high stress drops at the fault edges of the two major events, the M W 7.2 Darfield and M W 6.2 Christchurch earthquakes.  相似文献   

12.
In previous research, trace amplitudes of surface wave maxima recorded by undamped Milne seismographs were used to determine the surface-wave magnitudes Ms of large shallow earthquakes which occurred prior to 1912. For this purpose, the effective gain of these instruments was calibrated by using the surface-wave magnitudes Ms(GR) which were calculated from the unpublished worksheets for Seismicity of the Earth of Gutenberg and Richter. In this paper, the real quality of Ms(GR) is critically re-evaluated by using independent sets of data. It is found that Ms(GR) for the period 1904–1909 is considerably overestimated. The average excess from the real Ms is 0.5 units for 1904–1906, 0.4 for 1907, 0.3 for 1908–1909 and 0.0 for 1910–1912. This overestimation is so systematic and large that the previous results are all redetermined. The average effective gain of Milne instruments is revised to be 21.9; previously, the gain depended on Ms. This revision results in systematic reduction in the previously assigned magnitudes. The revised values of Ms for 264 shallow earthquakes, with Ms=6.8 and over in the period 1897–1912 inclusive, are listed. The present revision is large enough to preclude the possibility of the high activity of large shallow earthquakes around the turn of the century. The present results have a direct effect on all the magnitude catalogues of shallow earthquakes which occurred prior to 1909.  相似文献   

13.
Aftershock locations, source parameters and slip distribution in the coupling zone between the overriding North American and subducted Rivera and Cocos plates were calculated for the 22 January 2003 Tecomán earthquake. Aftershock locations lie north of the El Gordo Graben with a northwest-southeast trend along the coast and superimposed on the rupture areas of the 1932 (M w?=?8.2) and 1995 (M w?=?8.0) earthquakes. The Tecomán earthquake ruptured the northwest sector of the Colima gap, however, half of the gap remains unbroken. The aftershock area has a rectangular shape of 42?±?2 by 56?±?2?km with a shallow dip of roughly 12° of the Wadati-Benioff zone. Fault geometry calculated with the Náb??lek (1984) inversion procedure is: (strike, dip, rake)?=?(277°, 27°, 78°). From the teleseimic body wave spectra and assuming a circular fault model, we estimated source duration of 20?±?2?s, a stress drop of 5.4?±?2.5?MPa and a seismic moment of 2.7?±?.7?×?1020?Nm. The spatial slip distribution on the fault plane was estimated using new additional near field strong motion data (54?km from the epicenter). We confirm their main conclusions, however we found four zones of seismic moment release clearly separated. One of them, not well defined before, is located toward the coast down dip. This observation is the result of adding new data in the inversion. We calculated a maximum slip of 3.2?m, a source duration of 30?s and a seismic moment of 1.88?×?1020?Nm.  相似文献   

14.
Source parameters of the earthquakes of the Baikal rift system   总被引：1，自引：0，他引：1  
The dynamic parameters of the earthquake source—the seismic moment, the moment magnitude, the source radius, the stress drop, and the amplitude of displacement—are determined by the amplitude Fourier spectra of the body shear waves (S-waves) for 62 earthquakes of the Baikal rift system with the energy class of K P = 9.1–15.7. In the calculations I used the classical Brune model. The seismic moment of the earthquakes being investigated changes from 3.65 × 1011 N m to 1.35 × 1018 N m, and the radii of earthquake sources vary from 390 m to 1.84 km. The values of the drop in stress Δσ grow with an increase in the seismic moment up to 1.7 × 108 Pa. For the group of weak earthquakes (M w = 1.7–3.3), extremely low values of the drop in stress 103–104 Pa are observed. The maximum amplitude of displacement in the source amounts to 5.95 m. The empirical equations between the seismic moment and the other dynamic parameters of the source are determined. The regional dependence of the seismic moment and energy class is obtained: log M 0 ± 0.60 = 1.03K P + 3.17. The character of the relationship between the seismic moment and the corner frequency indicates that the classical scaling law of the seismic spectrum for the earthquakes in question is not fulfilled. The obtained estimates of the dynamic parameters are in satisfactory agreement with the published data concerning the analogous parameters of the other rift zones, which reflects the general regular patterns of the destruction of the lithosphere and the seismicity in the extension zones of the lithosphere.  相似文献   

15.
Over the last 25 years mining-induced seismicity in the Ruhr area has continuously been monitored by the Ruhr-University Bochum. About 1,000 seismic events with local magnitudes between 0.7 ≤ M L ≤ 3.3 are located every year. For example, 1,336 events were located in 2006. General characteristics of induced seismicity in the entire Ruhr area are spatial and temporal correlation with mining activity and a nearly constant energy release per unit time. This suggests that induced stresses are released rapidly by many small events. The magnitude–frequency distribution follows a Gutenberg–Richter relation which is a result from combining distributions of single longwalls that themselves show large variability. A high b-value of about 2 was found indicating a lack of large magnitude events. Local analyses of single longwalls indicate that various factors such as local geology and mine layout lead to significant differences in seismicity. Stress redistribution acts very locally since differences on a small scale of some hundreds of meters are observed. A regional relation between seismic moment M 0 and local magnitude M L was derived. The magnitude–frequency distribution of a single longwall in Hamm was studied in detail and shows a maximum at M L = 1.4 corresponding to an estimated characteristic source area of about 2,200 m2. Sandstone layers in the hanging or foot wall of the active longwall might fail in these characteristic events. Source mechanisms can mostly be explained by shear failure of two different types above and below the longwall. Fault plane solutions of typical events are consistent with steeply dipping fracture planes parallel to the longwall face and nearly vertical dislocation in direction towards the goaf. We also derive an empirical relation for the decay of ground velocity with epicenter distance and compare maximum observed ground velocity to local magnitude. This is of considerable public interest because about 30 events larger than M L ≥ 1.2 are felt each month by people living in the mining regions. Our relations, for example, indicate that an event in Hamm with a peak ground velocity of 6 mm/s which corresponds to a local magnitude M L between 1.7 and 2.3 is likely to be felt within about 2.3 km radius from the event.  相似文献   

16.
The time variations in the Gutenberg–Richter b-value are minutely studied based on the data of highly accurate seismological observations at the Garm prognostic site, Tajikistan, where a stationary network of seismic stations of the Complex Seismological Expedition (CSE) of Schmidt Institute of Physics of the Earth (IPE) of the USSR (Russian) Academy of Sciences was in operation from 1955 to 1992. A total of 93035 local earthquakes ranging from 0.0 to 6.3 in the Ml magnitudes are considered. The spatiotemporal fluctuations in the minimal magnitude of completeness of the earthquakes, Mc, are analyzed. The study considers a 25-year interval of the observations at the center of the observation system within which Mc = 0.9. It is shown that in most cases, the b-value and log10E2/3 experience characteristic time variations before the earthquakes with magnitudes higher than the minimal magnitude of the predicted earthquake (MPE). The 6-year anomaly in the parameters’ b-value, log10E2/3, and log10N associated with the single strongest earthquake with M = 6.3 that occurred in the observation region on October 26, 1984 is revealed. The inversely proportional relationship is established between the time variations in the b-value and the time variations in the velocities of seismic waves Vp and Vp/Vs. It is shown that the exponent p in the power function which links the time variations of the b-value and log10E2/3 is higher in the zones of crustal compression than in the zones of extension. It is simultaneously confirmed that the average b-value in the zones of compression is lower than in the zones of extension. It is established that in the case of earthquakes with M ≥ 2.6, the time series of seismic activity log10Ni and the time series of the b-value are highly cross correlated with a coefficient of r ≈ 0.75, whereas in the case of earthquakes with M ≥ 0.9, the coefficient of cross correlation between these time series is close to zero (r ≈ 0.06). The law of variations in the slope of the lines approximating the relationship between the log10Ni time series in the different magnitude ranges (M ≥ Mci) and b-value time series is obtained. It is hypothesized that the seismic activity of the earthquakes with high magnitudes can be estimated provided that the parameters of the time series of the b-value and time series of the number of earthquakes logN(ΔMi) in the range of low magnitudes are known. It is concluded that using the parameter log10N for prognostic estimates of the strong earthquakes only makes sense for earthquakes having moderate and large magnitudes. It is inferred that the time variations in the b-value are predominantly contributed by the time variations of the earthquakes with relatively large magnitudes.  相似文献   

17.
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   

18.
Substantial changes in the seismic regime of the Earth during 1982–1993 are revealed on the basis of a new methodological approach to the study of the development of global seismogeodynamic processes. These changes are a more than threefold decrease in the recurrence rate of large earthquakes in the magnitude intervals M = 8.5 ± 0.2, M = 8.0 ± 0.2, M = 7.5 ± 0.2, and M = 7.0 ± 0.2 and a very intense activation of global seismicity after this relative seismic quiescence. Joint investigations of seismogeodynamic and hydrogeodynamic processes allowed us to reveal a certain synchronism between changes in the seismic regime of the Earth and the ocean water surface level. In this paper, we continue the search for a relation between changes in the regional seismicity and the level of closed water basins (with the Caspian Sea as an example), as well as investigations of the processes in individual seismic sources, in order to elaborate earthquake prediction methods. Hypotheses on the nature of the discovered phenomena are put forward, and structural phenomenological models are proposed. In particular, these correlated seismic and hydrologic phenomena are interpreted in terms of specific features of the seismogeodynamic regime in subduction zones on the periphery of the Pacific and Indian oceans.  相似文献   

19.
The risk formula, expressing the probability of at least one occurrence of earthquakes of greater-than-design-value magnitudes over the economic life of a structure, is modified taking into consideration the probability of no-earthquake years. The annual maximum earthquake magnitudes of three scales: Richter magnitude, also known as local magnitude (ML), body-wave magnitude (Mb), and moment magnitude (MM) in a geographical area encompassing the Bingöl Province in Turkey are taken from two sources: (1) report by Kalafat et al. (2007) [14] and (2) the web site reporting data by Kandilli Observatory which has been recording earthquakes occurring in and around Turkey since 1900. Statistical frequency analyses are applied on the three sample series using various probability distribution models, and magnitude versus average return period relationships are determined. The values of the ML, Mb, and MM series for 10% and 2% risk are computed to be around 7.2 and 8.3. The tectonic structure and seismic properties of the Bingöl region are also given briefly.  相似文献   

20.
内蒙古中西部地区中小地震矩震级研究   总被引：1，自引：1，他引：0  
刘芳  张帆  李彬  娜热 《中国地震》2017,33(2):301-310
基于S震相"S窗"内的波形信号识别、品质因子Q(f)和22个台站场地响应,利用2009~2016年3月内蒙古中西部地区地震的波形资料,反演了182次中小地震的震源波谱参数,得到这些小震的零频幅值及其拐角频率,据此计算了这些地震的地震矩M_0、矩震级M_W和应力降Δσ。利用回归分析方法得到了近震震级与矩震级、矩震级与应力降的关系式。分析表明,近震震级与矩震级、矩震级与应力降呈线性关系。可见,将矩震级纳入地震的快报与正式目录中,可以丰富地震观测报告内容,更好地为地震应急和地震科研服务。  相似文献   

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