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1.
A vectorial modelling of observed macroseismic intensity aimed at the analytical determination of the epicentre is proposed here. The methodology is based on the determination of a plane system of vectors which characterises the macroseismic intensity distribution. The epicentre of each seismic event considered is determined as the centre of this vector system by an analytical expression which is independent from all possible directions of seismic energy propagation. The analysis of the intensity distribution is carried out by a new model called a macroseismic plane, different from the one known as macroseismic field, formed by a set of small areas built around the observed intensity points; hence its name.With the proposed methodology, some earthquakes in southern Italy and eastern Sicily are analysed calculating their epicentres, also for distributions of observed intensity which are particularly complex. 相似文献
2.
A methodology for the anisotropic characterization of macroseismic fields is proposed, in order to evaluate seismic hazard, based on the real geometry of the isoseismals of the field. The proposed methodology, independent of the macroseismic intensity attenuation law, allows both for a single field and for several fields in the same source zone, the determination of minimum and maximum attenuation values and of the relative directions. 相似文献
3.
The aim of this paper is to define the macroseismic field of the 5 May 1990 Potenza earthquake, analysing about 3000 questionnaire forms together with the results of the direct inquiries carried out in the field. The study evidences the seismic vulnerability of the Potenza district and of the whole of southern Italy in general, due to the low resistance characteristics of the old constructions and a lack of seismic prevention. Besides, geomorphological failure increases hazardous situations at the earthquake's occurrence. This earthquake provided a good test for checking and improving the ING macroseismic data collection procedures. 相似文献
4.
We demonstrate that the approximate source kinematics of the San Fernando, 1971 earthquake can be back-predicted by analysing its macroseismic intensity data set (felt reports) objectively and quantitatively. This is done by inverting either the data set of the intensity values observed in all sites, or the intensities tessellated with the Voronoi polygons technique. It is shown that the kinematic characteristics found following our method (epicentral coordinates, source depth, seismic moment, rupture length, Mach number, fault plane solution) match those determined by other authors, via instrumental measurements, rather well. The prerequisite for obtaining these results is that local amplification must not affect groups of neighboring sites. It was possible to invert the U.S.G.S. ``felt reports' for the source because this data set is sufficiently uncontaminated by local site responses, and retains relevant regional traces of source effects. Isoseismal maps cannot be safely used for this task, because qualitative drawing criteria give subjective results. Isoseismals, based on incomplete space frequency samplings, give rise to spurious effects, whereas the Voronoi polygons produce easy-to-grasp, quantitative and objective, representations of macroseismic intensity data. The tests performed, up to now on a series of earthquakes, suggest that the combined use of tessellation and of our KF model is promising mostly for inverting intensities of preinstrumental earthquakes. 相似文献
5.
Atlas of macroseismic maps for French earthquakes with their principal characteristics 总被引：1，自引：0，他引：1
The SIRENE macroseismic database has been utilized to draw isoseismal maps for the 140 best-documented French earthquakes, characterized by epicentral intensities of at least V (MSK) and located in all parts of the country. A study of focal depths derived from available local intensity data using an intensity versus distance decay law (Sponheuer) shows that the focal depths of most of the events considered do not exceed about 10 km. Their distribution correlates fairly well with regional dynamic geology features. A relationship is then computed between magnitude, intensity and focal distance, based on 73 instrumenta]ly recorded earthquakes (M
L
between 3.3 and 6.3) and on 217 mean radius values (from 2 to 380 km) for isoseismals of intensity VIII to III (MSK). This relationship is applied to historical earthquakes contained in the database SIRENE which are characterised by their intensity only. These results are used in the evaluation as well deterministic as probabilistic of the seismic hazard on the national territory. 相似文献
6.
Macroseismic intensity attenuation for crustal sources on romanian territory and adjacent areas 总被引：1，自引：0，他引：1
A. Pantea 《Natural Hazards》1994,10(1-2):65-72
The macroseismic intensity attenuation (m.i.a.) laws for the main seismic provinces with crustal foci of the Romanian territory and adjacent areas were established. The input data consist of MSK-64 intensities of 18 earthquakes with epicentral/maximum intensity in the range V to X degrees (MSK scale), whose isoseismal maps were available.The attenuation was analyzed as a function of distance and azimuth and from the three main attenuation formulas (logarithmic, exponential, and power-law) (the last one was preferred, as it best fits the observed data) and, consequently, were used for each seismogenic region. The bulk of derived equations is intended to be further used in the assessment of the seismic hazards of Romania. 相似文献
7.
A new mathematical model describing the field of macroseismic intensity has been elaborated. It is based on elliptic isoseismals. The orientation of the main axes of elliptic isoseismals depends on the direction of stretching of the main geological structures on the investigated territory.The new model of a macroseismic field was applied to the territory of Eastern Uzbekistan. Some results of macroseismic investigations of the effect of large regional earthquakes were used as initial data.A noncircular model of a macroseismic field was introduced into the integral of the seismic shakability of Riznichenko and, according to the model, a macroseismic shakability map for the territory of Eastern Uzbekistan was computed in isolines of the long-term mean return period of vibrations for the intensity I 8.Paper presented at the 21st General Assembly of the European Seismological Commission, Sofia, 1988. 相似文献
8.
We discuss historical evidence for seismicity on the southern margin of the Siberian craton collected from old local newspapers. The reported earthquakes vary in magnitude from M = 2.5 to 4.5, and their macroseismic locations agree well with the regional tectonic framework. The new data prove seismic activity in the area and can be used in seismic risk assessment. 相似文献
9.
Prognostic estimations of the expected number of killed or injured people and about the approximate cost associated with the damages caused by earthquakes are made following a suitable methodology of wide-ranging application. For the preliminary assessment of human life losses due to the occurrence of a relatively strong earthquake we use a quantitative model consisting of a correlation between the number of casualties and the earthquake magnitude as a function of population density. The macroseismic intensity field is determined in accordance with an updated anelastic attenuation law, and the number of casualties within areas of different intensity is computed using an application developed in a geographic information system (GIS) environment, taking advantage of the possibilities of such a system for the treatment of space-distributed data. The casualty rate, defined as the number of killed people divided by the number of inhabitants of the affected region, is also computed and we show its variation for some urban concentrations with different population density. For a rough preliminary evaluation of the direct economic cost derived from the damages, equally through a GIS-based tool, we take into account the local social wealth as a function of the gross domestic product of the country. This last step is performed on the basis of the relationship of the macroseismic intensity to the earthquake economic loss in percentage of the wealth. Such an approach to the human casualty and damage levels is carried out for sites near important cities located in a seismically active zone of Spain, thus contributing to an easier taking of decisions in emergency preparedness planning, contemporary earthquake engineering and seismic risk prevention. 相似文献
10.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(6):483-487
In the last years many studies were carried out in order to assess the correlation between nearsurface geology and seismic response of downtown Rome during local and regional earthquakes. Nevertheless, only historical macroseismic data and theoretical modelling could be used so far to estimate the ground motion in the historical part of the city. The occurrence of the October 14, 1997 Umbria Marche event (Mw = 5.7), located about 115 km far from Rome but largely felt in the city, allowed us to verify our knowledge of the seismic response on the basis of the present urban setting of Rome.A prompt macroseismic survey in the urban area within the ring-road (G.R.A.) was performed. 949 questionnaires were compiled by means of 1842 interviews: such a large amount of macroseismic information, for the first time available in Rome, was related to 669 observation points providing a picture of local intensity variations. The areal distribution of collected intensity points is quite homogeneous.The data analysis points out a preferential distribution of larger effects (65%) in correspondence of Holocene alluvium outcrops. Furthermore, a tight correspondence between remarkable intensities and alluvial sediments is pointed out in suburban areas characterized by the minor hydrographic network of the Tiber River. Macroseismic anomalies were outlined in sectors of the urban area where local hydrogeological conditions can be responsible for a significant deterioration of geomechanical properties. 相似文献
11.
An anisotropic attenuation law of the macroseismic intensity has been deduced, congruent with an anisotropic modelling of macroseismic fields. The results, obtained by analysing a set of earthquakes in Eastern Sicily and Southern Calabria, show a greater adaptability to the observed data as compared with those deduced using isotropic attenuation laws modified to take the anisotropy into account. 相似文献
12.
L. N. Poplavskaya T. V. Nagornykh O. A. Mel’nikov D. A. Safonov Kim Chun Un 《Russian Journal of Pacific Geology》2012,6(2):164-172
The results of the instrumental and macroseismic studies are reported for the tangible earthquake with intensity of up to
5–6 and amplitude of MLH = 4.8 that occurred near the western coast of Sakhalin Island. The main parameters of the Kostromskoe
earthquake have been estimated in two versions: (1) based on the data from the local network of digital stations located in
southern Sakhalin, and (2) from the complex of local, regional, and global observations. It has been noted that the development
of the local network in southern Sakhalin allowed the seismic regime in the earthquake area to be investigated in more detail
and the mechanisms of both the individual weak and group events to be derived. The acquired data on the dislocation style
of the main shock and aftershocks in the days following the event were used for the geological-tectonic interpretation of
the Kostromskoe earthquake. 相似文献
13.
This paper reappraises the seismicity of Algeria and adjacent regions. It presents a general view of the geographical structure, the historical development of the seismological station network, some aspects of the effects of past destructive earthquakes, the state of knowledge of the seismicity and the seismic hazard and risk in the region under survey. Magnitude-frequency relationships for different parts of the region studied are presented as well as magnitude-intensity and intensity-attenuation relationships, semi-empirical formula. It also discusses the macroseismic information, the instrumental data and the social and economic implications of earthquakes in the Maghreb region. 相似文献
14.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(6):477-481
Umbria-Marche region (Central Italy) has been interested by a seismic sequence, which caused a large amount of damage within an extensive area (around 5000 km2). The sequence produced eight shocks with magnitude higher than 5.0, the largest of them occurring on September 26, UTC 09:40, M1 = 5.8. The incidence of many shocks with a magnitude higher than 4.0 contributed to the creation of a damage pattern that was in evolution for more than one month. Such seismic behavior motivated field operators to perform a real-time macroseismic survey to update the data set. One of the major objectives was to differentiate the effects pertaining to each of the largest shocks. In this paper we present the macroseismic survey performed during the sequence, along with some preliminary results inferred. Intensity points of seven of the main shocks are shown, together with the filtered macroseismic fields produced following the application of specific statistical methods. Finally, consideration is given to the comparison of these study results with corresponding tectonic and geological data. 相似文献
15.
Sergio Espinosa 《Natural Hazards》1996,13(2):179-202
A probabilistic macroseismic hazard assessment has been done for Nicaragua. For this, the most complete catalogue for Central America, compiled by NORSAR in Norway has been used. In this catalogue, empirical intensity attenuation relations were found. Using these empirical relations, magnitudes were changed to epicentral intensities expected in sites where no intensities had been reported. The calculated intensities from a polygon surrounding Nicaragua were used to assess the macroseismic hazard in the region. For the whole polygon, the cumulative intensity frequency was calculated resulting in a b-value of 0.60 for an intensity interval of V–IX. The time completeness was also studied indicating that, for strong events causing higher intensities (I
0 VII), the catalogue is complete for events that have been recorded since 1840. The whole polygon was cut into independent seismotectonic regions where the statistical procedure (intensity frequency and time completeness) was done. 相似文献
16.
B. C. Papazachos Ch. A. Papaioannov D. J. Papastamatiou B. N. Margaris N. P. Theodulidis 《Natural Hazards》1990,3(2):141-151
Historical and present century instrumental data have been used to determine seismic hazard in 35 sites of Greece by the application of Cornell's method (Cornell, 1968) and the mean value method. The macroseismic intensity has been considered as a measure of seismic hazard. Comparison of the results of the two methods showed that, in general, the mean value method gives higher values, particularly for low probabilities of exceedance. In addition, for some sites, the differences of the expected intensities resulting from the two methods, indicate that finer tuning of the seismogenic souce model is required, or suggest time dependence. Although each one of these methods has its own merits, the method based on seismic zonation (Cornell's method) has several advantages and must be preferred when an accurate zonation is possible by the use of macroseismic and instrumental seismic data, together with geological and geomorphological information. However, reliable estimates of seismic hazard at a particular site require work on a microzoning scale, incorporating historical, archaeological, and recent geological data.Paper presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988. 相似文献
17.
Macroseismic Surveys in Theory and Practice 总被引：1，自引：0，他引：1
Macroseismology is the part of seismology that collects and evaluates non-instrumental data on earthquakes, i.e., effects on people, objects, buildings and nature. The methods that seismologists use for collecting and evaluating the macroseismic data are often based on long (trial-and-error) experience more than on some formal procedure. Until very recently manuals or guidelines on how to do a macroseismic survey were rare and often superficial. After an earthquake is felt in some region, the data are usually collected by means of questionnaires. Field survey is an obligatory tool that complements the questionnaires in the case of a damaging earthquake. An overview of the approaches to deriving the earthquake parameters (epicentre and barycentre, epicentral intensity, magnitude, depth, source parametres) from macroseismic data, as well as a review of some existing practices is given. 相似文献
18.
Hazard mapping based on macroseismic data considering the influence of geological conditions 总被引：1，自引：0，他引：1
The object of this study is to consider directly the influence of regional geological conditions on the assessment of seismic hazard. It is assumed that macroseismic data at individual locations contain, in an average way, the influence of geological conditions.A Data Base referring to 199 historical (5) and instrumental (194, in the 1947–1993 period) events with macroseismic information in 1195 locations of Portugal was built. For any given seismic event, whenever macroseismic information was available at a location (town, village, etc.), an EMS-92 intensity value was estimated. To each one of those locations a geological unit, representing the most common type of soil, was assigned, based on the Geological Portuguese Map at a scale 1:500 000; the geological units were grouped into three categories: soft, intermediate and hard soils.The Data Base was used to determine the attenuation laws in terms of macroseismic intensity for the three different geological site conditions, using multiple linear regression analysis. The reasonability of the laws was tested by (i) checking residual distributions and (ii) comparing the map of isoseismals of important earthquakes with the isoseismals generated by the attenuation curves derived for each one of the three different soil classes, taking into consideration the soil class of each site. The main results of attenuation modeling are: high dispersion on macroseismic intensity data; all the models predict intensity values, for short hypocentral distances, lower than the ones observed; and for some important analyzed earthquakes and for the observed range of distances, the models confirm the expectancy that macroseismic intensity increases from hard to soft soil.The approach to obtain the hazard assessment at each location consisted in the use of the attenuation law specifically derived for the class of soil of that particular location. This method, which considers the influence of the regional geology, was illustrated with the mapping of hazard for the country for several return periods. Comparison with previous maps not taking into consideration the regional geological conditions emphasizes the importance of this new parameter. It can be concluded that (i) soil segmentation is clearly the cause for hazard increase in the region to the north of Lisbon, especially at sites with soft and intermediate soils as the ones in lower Tagus valley; the maximum increase on hazard is, in any case, less than one degree; (ii) when geological conditions are disregarded in the attenuation regression analysis, hazard pattern is similar to the one obtained for the case of hard soil everywhere. 相似文献
19.
N. V. Shestakov D. A. Safonov N. S. Kovalenko S. A. Kasatkin S. M. Krasnopeyev M. D. Gerasimenko Guojie Meng 《Russian Journal of Pacific Geology》2018,12(1):46-56
Primorye is a region with quite moderate shallow seismicity which has been insufficiently investigated so far in this respect. Based on the obtained instrumental data of regional seismic networks and macroseismic data collected in southwestern Primorye on the crustal earthquake with M = 4.5 occurred on April 12, 2014, we have first succeeded in determining the hypocenter parameters and the focal mechanism of the mainshock of this shallow earthquake and estimating the hypocenter parameters of the following aftershock. 相似文献
20.
Generally the seismic hazard of an area of interest is considered independent of time. However, its seismic risk or vulnerability, respectively, increases with the population and developing state of economy of the area. Therefore, many areas of moderate seismic hazard gain increasing importance with respect to seismic hazard and risk analysis. However, these areas mostly have a weak earthquake database, i.e., they are characterised by relative low seismicity and uncertain information concerning historical earthquakes. In a case study for Eastern Thuringia (Germany), acting as example for similar places in the world, seismic hazard is estimated using the probabilistic approach. Because of the lack of earthquakes occurring in the recent past, mainly historical earthquakes have to be used. But for these the actual earthquake sources or active faults, needed for the analysis, are imprecisely known. Therefore, the earthquake locations are represented by areal sources, a common practice. The definition of these sources is performed carefully, because their geometrical shape and size (apart from the earthquake occurrence model) influence the results significantly. Using analysis tools such as density maps of earthquake epicentres, seismic strain and energy release support this. Oversizing of areal sources leads to underestimation of seismic hazard and should therefore be avoided. Large location errors of historical earthquakes on the other hand are represented by several alternative areal sources with final superimposition of the different results. In a very similar way information known from macroseismic observations interpreted as source rather than as site effects are taken into account in order to achieve a seismic hazard assessment as realistic as possible. In very local cases the meaning of source effects exceeds those of site effects very likely. The influence of attenuation parameter variations on the result of estimated local seismic hazard is relatively low. Generally, the results obtained by the seismic hazard assessment coincide well with macroseismic observations from the thoroughly investigated largest earthquake in the region. 相似文献