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1.
In this work, the macroseismic effects of the Kultuk earthquake (M W = 6.3), which took place on August 27, 2008 in the southwestern closure of the Baikal Lake, are under consideration. The intensity of shocks in inhabited localities located in the epicentral zone reached 7–8 points on the MSK-64 scale. The earthquake was named after the local settlement of Kultuk, which was the mostly damaged area by the earthquake. The considered seismic event caused significant material damage (about 250 million rubles according to preliminary estimates). In inhabited localities of Southern Pribaikalie thousands of cases of damaged ovens and chimneys were registered. Some buildings were highly damaged and, accordingly, they are unfit for further use. The earthquake was the cause of numerous rockslides, rockfalls, and landslides on steep natural and artificial slopes. A macroseismic survey allowed us to establish the asymmetrical distribution of the intensity of shocks relative to the epicenter.  相似文献   

2.
We model the macroseismic damage distribution of four important intermediate-depth earthquakes of the southern Aegean Sea subduction zone, namely the destructive 1926 M?=?7.7 Rhodes and 1935 M?=?6.9 Crete earthquakes, the unique 1956 M?=?6.9 Amorgos aftershock (recently proposed to be triggered by a shallow event), and the more recent 2002 M?=?5.9 Milos earthquake, which all exhibit spatially anomalous macroseismic patterns. Macroseismic data for these events are collected from published macroseismic databases and compared with the spatial distribution of seismic motions obtained from stochastic simulation, converted to macroseismic intensity (Modified Mercalli scale, IMM). For this conversion, we present an updated correlation between macroseismic intensities and peak measures of seismic motions (PGA and PGV) for the intermediate-depth earthquakes of the southern Aegean Sea. Input model parameters for the simulations, such as fault dimensions, stress parameters, and attenuation parameters (e.g. back-arc/along anelastic attenuation) are adopted from previous work performed in the area. Site-effects on the observed seismic motions are approximated using generic transfer functions proposed for the broader Aegean Sea area on the basis of VS30 values from topographic slope proxies. The results are in very good agreement with the observed anomalous damage patterns, for which the largest intensities are often observed at distances >?100 km from the earthquake epicenters. We also consider two additional “prediction” but realistic intermediate-depth earthquake scenarios, and model their macroseismic distributions, to assess their expected damage impact in the broader southern Aegean area. The results suggest that intermediate-depth events, especially north of central Crete, have a prominent effect on a wide area of the outer Hellenic arc, with a very important impact on modern urban centers along northern Crete coasts (e.g. city of Heraklion), in excellent agreement with the available historical information.  相似文献   

3.
A disastrous earthquake with a magnitude M S = 8.0 (M W = 7.9), in China called “the 5.12 Wenchuan earthquake,” occurred on May 12, 2008, in Sichuan province on the border between the Sino-Tibetan Mountains and the Sichuan depression. The instrumental epicenter was registered in the southeastern part of Wenchuan county, and the hypocenter depth was 14 km. As the strongest and most destructive earthquake within mainland China, it caused numerous human losses and destruction of buildings and infrastructure. The seismic effect from the main shock and aftershocks was felt in many counties, towns, and villages, though Sichuan province suffered the most. The maximum intensity of the shocks was estimated at 11 degrees, according to the Chinese macroseismic scale. In the process of source opening, from the southern part of Wenchuan county to the vicinities of Quingchuan, a seismic fault system with a total length up to 240 km out-cropped on the earth’s surface, confined to the Longmenshan fault belt. The seismic fault system disturbed the original ground, resulting in the collapse or damage to various constructions, such as buildings, homes, bridges, roads, etc. Fault offsets had a dextral strike-slip and thrust kinematic combination. The earthquake generated several tens of thousands of landslides, rockfalls, and debris flows. Many dammed ponds appeared in the epicentral zone due to the activation of landslides. Thus, the geological effects turned out to be the most destructive factor in this case. At the same time, the seismic intensity of surface shaking was abnormally low even in direct proximity to the seismic fault system. Usually it was no more than 7–8 degrees. This macroseismic phenomenon may turn out to be rather typical for many major earthquakes.  相似文献   

4.
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   

5.
Upgrading the Earthquake Catalog of Switzerland (ECOS) included revising the earthquake of 1720. This change has major importance for history and seismology.Although that quake has been the subject of several publications, none was based on critical methods. This re-evaluation of the event is built upon a new and more reliable database established after investigating archives and libraries. Using data from such historical sources, we assigned new site intensities, adopting the criteria established by the European macroseismic scale EMS 98 (Grünthal, 1998).We discovered that the event had been assigned an overestimated intensity, due to interpretation errors in former earthquake catalogs and compilations. We recommend reducing the intensity from I0= VIII to I0= VI (EMS 98). The moment magnitude is given as MW= 4.6. Since the event had been considered the largest for its respective area, downgrading it now will influence the seismic hazard assessment for this region.  相似文献   

6.
根据地震现场宏观烈度调查资料,介绍了1999年3月25日广东河源市M  相似文献   

7.
We present the results of probabilistic seismic hazard assessment for Iceland in the framework of the EU project UPStrat-MAFA using the so-called site approach implemented in the SASHA computational code. This approach estimates seismic hazard in terms of macroseismic intensity by basically relying on local information about documented effects of past seismic events in the framework of a formally coherent and complete treatment of intensity data. In the case of Iceland, due to the lack of observed intensities for past earthquakes, local seismic histories were built using indirect macroseismic estimates deduced from epicentral information through an empirical attenuation relationship in probabilistic form. Seismic hazard was computed for four exceedance probabilities for an exposure time of 50 years, equivalent to average return periods of 50, 200, 475 and 975 years. For some localities, further return periods were examined and deaggregation analysis was performed. Results appear significantly different from previous seismic hazard maps, though just a semi-qualitative comparison is possible because of the different shaking measure considered (peak ground acceleration versus intensity), and the different computational methodology and input data used in these studies.  相似文献   

8.
On October 27, 2004, a moderate size earthquake occurred in the Vrancea seismogenic region (Romania). The Vrancea seismic zone is an area of concentrated seismicity at intermediate depths beneath the bending area of the southeastern Carpathians. The 2004 M w?=?6 Vrancea subcrustal earthquake is the largest seismic event recorded in Romania since the 1990 earthquakes. With a maximum macroseismic intensity of VII Medvedev–Sponheuer–Kárník (MSK-64) scale, the seismic event was felt to a distance of 600 km from the epicentre. This earthquake caused no serious damage and human injuries. The main purpose of this paper is to present the macroseismic map of the earthquake based on the MSK-64 intensity scale. After the evaluation of the macroseismic effects of this earthquake, an intensity dataset has been obtained for 475 sites in the Romanian territory. Also, the maximum horizontal accelerations recorded in the area by the K2 network are compared to the intensity values.  相似文献   

9.
Ground motion prediction equations (GMPE) in terms of macroseismic intensity are a prerequisite for intensity-based shake maps and seismic hazard assessment and have the advantage of direct relation to earthquake damage and good data availability also for historical events. In this study, we derive GMPE for macroseismic intensity for the Campania region in southern Italy. This region is highly exposed to the seismic hazard related to the high seismicity with moderate- to large-magnitude earthquakes in the Appenninic belt. The relations are based on physical considerations and are easy to implement for the user. The uncertainties in earthquake source parameters are accounted for through a Monte Carlo approach and results are compared to those obtained through a standard regression scheme. One relation takes into account the finite dimensions of the fault plane and describes the site intensity as a function of Joyner–Boore distance. Additionally, a relation describing the intensity as a function of epicentral distance is derived for implementation in cases where the dimensions of the fault plane are unknown. The relations are based on an extensive dataset of macroseismic intensities for large earthquakes in the Campania region and are valid in the magnitude range M w = 6.3–7.0 for shallow crustal earthquakes. Results indicate that the uncertainties in earthquake source parameters are negligible in comparison to the spread in the intensity data. The GMPE provide a good overall fit to historical earthquakes in the region and can provide the intensities for a future earthquake within 1 intensity unit.  相似文献   

10.
The macroseismic field of the Balkan area   总被引：1，自引：0，他引：1  
A catalogue of 356 macroseimic maps which are available for the Balkan area was compiled, including information on the source parameters of the corresponding earthquakes, the macroseismic parameters of their strength and their macroseismic field. The data analysis of this catalogue yields new empirical relations for attenuation, which can be applied for the calibration of historical events, modelling of isoseismals and seismic hazard assessment. An appropriate analysis allowed the separation and estimation of the average values of the geometrical spreading, n, and anelastic attenuation factor, c, for the examined area which were found equal to –3.227 ± 0.112 and –0.0033 ± 0.0010. Scaling relations for the focal macroseismic intensity, If, and the epicentral intensity I0, versus the earthquake moment magnitude were also determined for each Balkan country. A gradual decrease of the order of 0.5 to 1 intensity unit is demonstrated for recent (after 1970) earthquakes in Greece. Finally the depths of the examined earthquakes as they robustly determined (error <5 km) on the basis of macroseismic data were found to have small values ( 10 km). However large magnitude earthquakes show higher focal depths ( 25 km), in accordance with an increase of the seismic fault dimensions for such events.  相似文献   

11.
The quantification and prediction of damage due to different seismic actions to structure types of different strength is an important problem not yet solved in the Earthquake Engineering field. In addition, owing to the fact that macroseismic information cannot be used directly in dynamic calculations, a new problem appears when these are the only kind of data available. Thus, there is a need to estimate a parameter to relate the energy of the ground motion and the damage occurrence, and eventually achieve a better seismic risk assessment. After the study and review of some representative potential damage parameters, attention has been paid to the Arias intensity (unfiltered and filtered in certain frequency ranges) and the Cumulative Absolute velocity (CAV) as the parameters to evaluate the energy of movement, and to relate them with the observed damage. The data used to infer these correlations have been provided by the ENEA-ENEL (Italy). The information consists of strong motion records from the Campano Lucano (1980), Umbria (1984) and Lazio-Abruzzo (1984) earthquakes, and data of damage to buildings in the vicinity of recording instruments (within a maximum radius of 300 m, where the soil conditions remain constant). In this paper, some relations have been obtained to quantify the damage level for different seismic inputs. The results suggest that unfiltered Arias intensity and CAV (for calculation threshold 20 cm/s2) correlate well with the macroseismic information used. Best fits are obtained between the quoted parameters and the observed damage in type A structures. © 1997 by John Wiley & Sons, Ltd.  相似文献   

12.
The 23 April 1909 earthquake, with epicentre near Benavente (Portugal), was the largest crustal earthquake in the Iberian Peninsula during the twentieth century (M w = 6.0). Due to its importance, several studies were developed soon after its occurrence, in Portugal and in Spain. A perusal of the different studies on the macroseismic field of this earthquake showed some discrepancies, in particular on the abnormal patterns of the isoseismal curves in Spain. Besides, a complete list of intensity data points for the event is unavailable at present. Seismic moment, focal mechanism and other earthquake parameters obtained from the instrumental records have been recently reviewed and recalculated. Revision of the macroseismic field of this earthquake poses a unique opportunity to study macroseismic propagation and local effects in central Iberian Peninsula. For this reasons, a search to collect new macroseismic data for this earthquake has been carried out, and a re-evaluation of the whole set has been performed and it is presented here. Special attention is paid to the observed low attenuation of the macroseismic effects, heterogeneous propagation and the distortion introduced by local amplifications. Results of this study indicate, in general, an overestimation of the intensity degrees previously assigned to this earthquake in Spain; also it illustrates how difficult it is to assign an intensity degree to a large town, where local effects play an important role, and confirms the low attenuation of seismic propagation inside the Iberian Peninsula from west and southwest to east and northeast.  相似文献   

13.
A multifractal analysis of seismicity of three large earthquakes in Chile is made: the Central Zone 1985 (M W = 8.0), Antofagasta 1995 (M W = 8.1), and Maule 2010 (M W = 8.8) earthquakes. The analysis shows that the fractal dimension spectrum D q decreases with time before an earthquake. This fact suggests that the spatial distribution of seismic events could form a cluster before a main shock.  相似文献   

14.
In many countries such as Spain earthquake databases still mainly comprise macroseismic data from felt effects. The full exploit of this information is of basic importance for seismic risk assessment and emergency planning, given the strict link between macroseismic intensity and damage. A probabilistic procedure specifically developed to handle macroseismic data, mostly relying on site information and seismogenic-source free, has been applied to evaluate seismic hazard in SE-Spain (Alicante-Murcia region). Present seismicity is moderate-low with largest magnitudes slightly over Mw5.0. The historical record includes very destructive earthquakes, maximum EMS98 intensities reaching IX–X and X in the nineteenth century (e.g., Torrevieja 1829 earthquake). Very recently, two events in the area on 11 May 2011 (Mw4.5, Mw5.2) killed nine people, injured 300, and produced important damage in the city of Lorca. Regional hazard maps for the area together with specific hazard curves at selected localities are obtained. Results are compared with the maximum observed intensities in the period 1300–2012, and with the values in the seismic hazard map from the Spanish Building Code in force. In general, the maximum felt intensity values are closer to the hazard values calculated for 2 % probability of exceedance in 50 years, using felt and expected intensity. The intensity-based probabilistic hazard maps obtained through the applied approach reduce the inherent smoothing of those based on standard probabilistic seismic hazard assessment approaches for the region, allowing identifying possible over- or sub-estimates of site hazard values, providing very valuable information for risk reduction strategies or for future updates of the building code hazard maps.  相似文献   

15.
On September 6, 2002, a ML = 5.6 earthquake, occurring some tens of kilometres offshore from the Northern Sicilian coast (Southern Tyrrhenian Sea), slightly damaged the city of Palermo and surroundings (degree 6 in the European Macroseismic Scale 1998). The macroseismic investigation of the shock and a detailed study of effects of the main earthquakes which affected Palermo in the past have been performed in order to evaluate the seismic response of the city. Moreover, the comparison of the recent event, which is instrumentally constrained, with historical earthquakes allows us to infer new insights on the seismogenic sources of the area, that seem located offshore in the Tyrrhenian sea.In the last 500 years, Palermo has never been completely destroyed but has suffered effects estimated between intensities 6 and 8 EMS-98 many times (1693, 1726, 1751, 1823, 1940, 1968, 2002). The damage scenarios of the analysed events have shown that damage distribution is strongly conditioned by soil response in the different parts of the city and by a high building vulnerability, mainly in the historical centre and in the south-eastern zone of the modern city. As a matter of fact, Palermo has always suffered greater effects than those reported for other nearby localities. The hazard assessment obtained using observed site intensities has shown that the probability of occurrence for intensity 8 (the strongest intensity observed in Palermo) exceeds 99% for 550 years, while the estimated mean return period is 152 ± 40 years. These results, in connection with building vulnerability due to the urban expansion before the introduction of seismic code, suggest that the city is exposed to a relatively high seismic risk.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first 3 months after its submission to Journal of Seismology.  相似文献   

16.
In regions that undergo low deformation rates, as is the case for metropolitan France (i.e. the part of France in Europe), the use of historical seismicity, in addition to instrumental data, is necessary when dealing with seismic hazard assessment. This paper presents the strategy adopted to develop a parametric earthquake catalogue using moment magnitude Mw, as the reference magnitude scale to cover both instrumental and historical periods for metropolitan France. Work performed within the framework of the SiHex (SIsmicité de l’HEXagone) (Cara et al. Bull Soc Géol Fr 186:3–19, 2015. doi: 10.2113/qssqfbull.186.1.3) and SIGMA (SeIsmic Ground Motion Assessment; EDF-CEA-AREVA-ENEL) projects, respectively on instrumental and historical earthquakes, have been combined to produce the French seismic CATalogue, version 2017 (FCAT-17). The SiHex catalogue is composed of ~40,000 natural earthquakes, for which the hypocentral location and Mw magnitude are given. In the frame of the SIGMA research program, an integrated study has been realized on historical seismicity from intensity prediction equations (IPE) calibration in Mw detailed in Baumont et al. (submitted) companion paper to their application to earthquakes of the SISFRANCE macroseismic database (BRGM, EDF, IRSN), through a dedicated strategy developed by Traversa et al. (Bull Earthq Eng, 2017. doi: 10.1007/s10518-017-0178-7) companion paper, to compute their Mw magnitude and depth. Macroseismic data and epicentral location and intensity used both in IPE calibration and inversion process, are those of SISFRANCE without any revision. The inversion process allows the main macroseismic field specificities reported by SISFRANCE to be taken into account with an exploration tree approach. It also allows capturing the epistemic uncertainties associated with macroseismic data and to IPEs selection. For events that exhibit a poorly constrained macroseismic field (mainly old, cross border or off-shore earthquakes), joint inversion of Mw and depth is not possible, and depth needs to be fixed to calculate Mw. Regional a priori depths have been defined for this purpose based on analysis of earthquakes with a well constrained macroseismic field where joint inversion of Mw and depth is possible. As a result, 27% of SISFRANCE earthquake seismological parameters have been jointly inverted and for the other 73% Mw has been calculated assuming a priori depths. The FCAT-17 catalogue is composed of the SIGMA historical parametric catalogue (magnitude range between 3.5 up to 7.0), covering from AD463 to 1965, and of the SiHex instrumental one, extending from 1965 to 2009. Historical part of the catalogue results from an automatic inversion of SISFRANCE data. A quality index is estimated for each historical earthquake according to the way the events are processed. All magnitudes are given in Mw which makes this catalogue directly usable as an input for probabilistic or deterministic seismic hazard studies. Uncertainties on magnitudes and depths are provided for historical earthquakes following calculation scheme presented in Traversa et al. (2017). Uncertainties on magnitudes for instrumental events are from Cara et al. (J Seismol 21:551–565, 2017. doi: 10.1007/s10950-016-9617-1).  相似文献   

17.
Synthetic isoseismals of three earthquakes in California and Nevada   总被引：1，自引：0，他引：1  
Recent tests on a series of earthquakes in California and Nevada suggest that in some regions the approximate shapes of the territories with equal earthquake-induced damage (expressed in terms of macroseismic intensity) could be synthetically traced out with a simple formula. This formula takes into account some gross features of the source: depth and length, unilateral or bilateral rupture, radiation patterns, rupture velocity, and directivity. Having been formulated on an empirical basis, the formula is however compatible with the so-called asymptotic approach, in which the far-field component of the Green's function is used. This paper presents the synthetic isoseismals of the earthquakes at Cedar Mountain, Nevada, 1932; Fairview Peak-Dixie Valley, Nevada, 1954; and Coalinga, California, 1983. An overall consistency, from acceptable to remarkable, between the observed intensity patterns and the synthetically back-predicted intensity has been obtained for them. Where the detailed modelling techniques available today are inapplicable, due to insufficient information on the features of the seismic sources, or to save time and money, the new formula may be utilizable for improving seismic hazard calculations.The formula was also used inversely for back-predicting geometric-kinematic parameters of the Coalinga 1983 earthquake from macroseismic maps. This gave characteristics for its source which are in good agreement with the majority of data inferred from modelling and from analyzing modern instrumental recordings. This striking result opens new perspectives in retrieving information on the source of ancient earthquakes for which only macroseismic information is available.  相似文献   

18.
It has been the belief among Earth scientists that the Peninsular Shield is aseismic, as the region attained stability long ago. However, the earthquake at Koyna (10 December 1967), Bhadrachalam (13 April 1969), Broach (23 March 1970), Hyderabad (30 June 1983), Khillari (30 September 1993), Jabalpur (22 May 1997), Gujarat (26 January 2001), and additional ones of smaller magnitudes, altered this concept. This area has experienced many widely distributed shallow earthquakes, some of them having large magnitudes. It is now widely accepted that seismic activity still continues with moderate events. Therefore, a need has arisen to take into consideration recent seismological data to assess the future seismic status of Peninsular India. Earthquake generation model has been studied to develop the statistical relations with surface wave magnitude (M S ≥ 4.5). Five seismogenic sources showing clustering of earthquakes and including at least three main shocks of magnitude 4.5 ≤ M S ≤ 6.5 giving two repeat times, have been identified. It is mainly based on the so-called “regional time-predictable model”. For the considered region it is observed that the time interval between two consecutive main shocks depends on the preceding main shock magnitude (M p ) not on the following main shocks magnitude M f suggesting the validity of time predictable model in the region.  相似文献   

19.
The estimation of the seismological parameters of historical earthquakes is a key step when performing seismic hazard assessment in moderate seismicity regions as France. We propose an original method to assess magnitude and depth of historical earthquakes using intensity data points. A flowchart based on an exploration tree (ET) approach allows to apply a consistent methodology to all the different configurations of the earthquake macroseismic field and to explore the inherent uncertainties. The method is applied to French test case historical earthquakes, using the SisFrance (BRGM, IRSN, EDF) macroseismic database and the intensity prediction equations (IPEs) calibrated in the companion paper (Baumont et al. Bull Earthq Eng, 2017). A weighted least square scheme allowing for the joint inversion of magnitude and depth is applied to earthquakes that exhibit a decay of intensity with distance. Two cases are distinguished: (1) a “Complete ET” is applied to earthquakes located within the metropolitan territory, while (2) a “Simplified ET” is applied to both, offshore and cross border events, lacking information at short distances but disposing of reliable data at large ones. Finally, a priori-depth-based magnitude computation is applied to ancient or poorly documented events, only described by single/sporadic intensity data or few macroseismic testimonies. Specific processing of “felt” testimonies allows exploiting this complementary information for poorly described earthquakes. Uncertainties associated to magnitude and depth estimates result from both, full propagation of uncertainties related to the original macroseismic information and the epistemic uncertainty related to the IPEs selection procedure.  相似文献   

20.
The earthquakes offshore Fujian and Guangdong Provinces concentrated along the two segments near Nan’ao in the south and Quanzhou in the north of the off coast fault, which is very active since the late Pleistocene. In 1918 and 1906, two earthquakes with magnitudes 7.3 and 6.1 respectively occurred in the south and the north regions. With the instrumentally determined seismic parameters of these two earthquakes as standards, the author evaluated the parameters of the historical earthquakes by comparing their macroseismic materials with consideration of the geological background. As a result, chronological tables of historical earthquakes of the south and the north regions were compiled. The seismic activity of the two regions synchronized basically, and their strongest recorded earthquakes were both aroundM s 7.3. Seismic activity usually intensified before the occurrence of strong events. Aftershocks were frequent, but strong aftershocks usually occurred one to several years after the main shock. Two high tides of seismic activity occurred since the late 15th century. Around 1600, eight earthquakes each with magnitudes over 4.3 occurred in both of the two regions. The magnitude of the strongest shock in the south region is 6.7, that in the north region is 7.5. The second high tide occurred at the early 20th century. Among the 18 earthquakes occurred in the south region, one was of magnitude 7.3; whilst only two earthquakes with magnitudes 6.1 and 5.5 respectively occurred in the north region. Further, medium to strong earthquakes never occurred since 1942. Whether this is the “mitigation effect” of strong shocks, or a big earthquake is brewing in the north region is worth intensive study. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 505–515, 1991. This work is supported by Chinese Joint Seismological Science Foundation.  相似文献   

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