scholarly journals TESTING THE MACROSEISMIC INTENSITY ATTENUATION RELATIONSHIPS FOR VRANCEA (ROMANIA) SUBCRUSTAL EARTHQUAKES IN RELATION WITH DAMS SITUATED IN EXTRA-CARPATHIAN AREA

2020 ◽  
Vol 2 (2) ◽  
pp. 17-34
Author(s):  
Angela Petruta Constantin ◽  
Elena Florinela Manea ◽  
Iren Adelina Moldovan ◽  
Raluca Partheniu
Keyword(s):  
Seismogenic Zone ◽  
Seismic Events ◽  
Intensity Attenuation ◽  
Attenuation Relationships ◽  
Test Intensity ◽  
Eastern Carpathians ◽  
Macroseismic Effects ◽  
Epicentral Intensity ◽  
Subcrustal Earthquakes ◽  
Attenuation Laws

The aim of the present paper is to test intensity attenuation relationships for subcrustal earthquakes occurred in Vrancea (Romania) seismogenic zone in relation with some important dams situated in extra-Carpathian area. During centuries, the Romanian territory has been shaken by strong earthquakes, most of them being centered within Vrancea Zone, which is situated at the bending area of the South-Eastern Carpathians. Most of the zones from extra-Carpathian area are affected by the subcrustal seismic events, where many hydro-technical structures exist, being also exposed to earthquakes action. A detailed analysis of the intensity attenuation laws developed for subcrustal seismic sources was performed using the most recent and complete intensity datasets. We use an extended and combined intensity data including historical and modern, qualitative and quantitative data, i.e. a number of 11 earthquakes occurred during the period 1738-2009 with epicentral/maximum intensities ranging from VII-X MSK degrees, and magnitude Mw from 5.4 to 7.9. All the input data used for testing are resulted after the reevaluation and evaluation of the macroseismic effects produced by the seismic events included in the present study (8697 IDP). The selected attenuation laws were tested for different values of epicentral intensity and with reference to twelve and twenty four azimuthal directions. Besides the testing of the relationships, isoseismal maps based on the selected attenuation laws were accomplished, associated to the biggest possible earthquake (worst scenario) for the Vrancea subcrustal zone, also highlighting the calculated intensities in the selected dam sites. Brief description of the study and used methods. Brief description of the study and used methods.

scholarly journals Testing and Developing the Macroseismic Intensity Attenuation Relationships for the Vrancea (Romania) Crustal Earthquakes

2019 ◽  
Vol 362 ◽  
pp. 012058
Author(s):  
Constantin Angela Petruta ◽  
Moldovan Iren-Adelina ◽  
Partheniu Raluca ◽  
Manea Elena Florinela ◽  
Ionescu Constantin
Keyword(s):  
Macroseismic Intensity ◽  
Intensity Attenuation ◽  
Attenuation Relationships ◽  
Crustal Earthquakes

scholarly journals The damaging character of shallow 20th century earthquakes in the Hainaut coal area (Belgium)

2021 ◽  
Author(s):  
Thierry Camelbeeck ◽  
Koen Van Noten ◽  
Thomas Lecocq ◽  
Marc Hendrickx
Keyword(s):  
Ground Motion ◽  
20Th Century ◽  
Focal Depth ◽  
Seismic Events ◽  
Late 20Th Century ◽  
Small Magnitude ◽  
Close Link ◽  
Epicentral Intensity ◽  
The 19Th Century ◽  
The Impact

Abstract. Shallow, light to moderate magnitude earthquakes in stable continental regions can have a damaging impact on vulnerable surface constructions. In the coal area of the Hainaut province in Belgium, a century of shallow seismic activity occurred from the end of the 19th century until the late 20th century. This seismicity is the second largest source of seismic hazard in northwestern Europe, after the Lower Rhine Embayment. The present study synthesises the impact and damage caused by this unique shallow seismicity. Reviewing intensity data provided in official macroseismic surveys held by the Royal Observatory of Belgium, press reports, and contemporary scientific studies resulted in a complete macroseismic intensity dataset. The strong shaking of five seismic events with moment magnitudes Mw around 4.0, which occurred on 3 June 1911, 3 April 1949, 15 December 1965, 16 January 1966, and 28 March 1967, locally caused widespread moderate damage to buildings corresponding to maximum intensity VII in the EMS-98 scale. For 28 earthquakes, detailed macroseismic maps were created. Our study highlights the capability of shallow, small-magnitude earthquakes to generate damage. Subsequently, using the Hainaut intensity dataset, we modelled a new Hainaut intensity attenuation law and created relationships linking magnitude, epicentral intensity and focal depth. Using these relationships, we estimated the location and magnitude of pre-1985 earthquakes that occurred prior to deployment of the modern digital Belgian seismic network. Estimated focal depths allowed discriminating between two different types of earthquakes. Some events were very shallow, only a few hundred metres deep, suggesting a close link to mining activities. Other earthquakes, including the largest and most damaging events, occurred at depths greater than 2 km but no deeper than 6 km, which would exclude a direct relationship with mining, but yet still might imply a triggering causality. This work results in a new updated earthquake catalogue including 123 seismic events. Our attenuation modelling moreover suggests that current hazard maps overestimated ground motion levels in the Hainaut area due to the use of inadequate ground motion prediction equations. Our Hainaut attenuation model is hence useful to evaluate the potential impact of current and future, e.g. geothermal energy, projects in the Hainaut area and other regions with a similar geological configuration.

scholarly journals Present-day stress field pattern in the Vrancea seismic zone (Romania) deduced from earthquake focal mechanism inversion

2021 ◽  
Vol 64 (6) ◽  
pp. PE660
Author(s):  
Andrei Bala ◽  
Mircea Radulian ◽  
Dragos Toma-Danila
Keyword(s):  
Large Strain ◽  
Average Energy ◽  
Seismogenic Zone ◽  
Field Pattern ◽  
Seismic Zone ◽  
Depth Level ◽  
Stress Regime ◽  
Intermediate Depth ◽  
Eastern Carpathians ◽  
Earthquake Focal Mechanism

   Vrancea seismogenic zone in the South-Eastern Carpathians is characterized by localized intermediate-depth seismicity. Due to its complex geodynamics and large strain release, Vrancea represents a key element in the Carpatho-Pannonian system. Data from a recently compiled catalogue of fault plane solutions (REFMC) are inverted to evaluate stress regime in Vrancea on depth. A single predominant downdip extensive regime is obtained in all considered clusters, including the crustal layers located above the Vrancea slab. The prevalent stress regime confirms previous investigations and requires some mantle-crust coupling. The S3 principal stress is close to vertical, while S1 and S2 are horizontal, oriented perpendicularly and respectively tangentially to the Carpathians Arc bend. This configuration is present at any depth level. According to seismicity patterns, there are two main active segments in the Vrancea intermediate-depth domain, at 55 – 105 km and 105 – 180 km, both able to generate major events. The configuration of the tectonic stresses as resulted from inversion is similar in both segments. Also, high fault instability (I > 0.95) is characterizing the segments. The only notable difference is given by the friction and stress ratio parameters which drop down in the bottom segment from μ = 0.95 to μ = 0.55 and from R = 0.51 to R = 0.29. This variation is attributed to possible weakening processes activated below 100 km depth and can explain the intensification of seismicity production as earthquake rate and average energy release in the lower segment versus the upper segment. 

scholarly journals Historical cities and earthquakes: Florence during the last nine centuries and evaluations of seismic hazard

1995 ◽  
Vol 38 (5-6) ◽  
Author(s):  
E. Guidoboni ◽  
G. Ferrari
Keyword(s):  
Seismic Hazard ◽  
Preliminary Analysis ◽  
Seismic Intensity ◽  
Seismic Events ◽  
Economic Resource ◽  
Artistic Value ◽  
12Th Century ◽  
Future Earthquake ◽  
The City ◽  
Attenuation Laws

The authors' aim in the following study is to contribute to the assessment of the seismic hazard of historical cities. From this preliminary analysis the general characteristics of the seismicity affecting Florence and the evaluation of its seismic hazard may be deduced. Florence is a <<mythical>> city of world tourism, and its extraordinary artistic value and its ability to be utilized constitute a great economic resource. From this perspective, the authors have tackled some aspects of its urban features (demography and main building types, successive phases in the growth of the city, etc.), aimed at the pooling of information as a basis for further, more specific analyses of seismic risk. The study is based on a review of 131 seismic events of potential interest for the site of Florence from the 12th century. In the case of each of these earthquakes, it was possible to verify the real seismic effects sustained, and thus to assess the seismic intensity on the site. This also enabled the limits in the application of the standard attenuation laws of to be checked. Of all the earthquakes analyzed. those which caused the greatest effects on the urban area have also been identified: namely, the earthquake of 28 September 1453. and those of 18 May and 6 June 1895, both with Io=VIII MCS. From their overall analysis the authors have further extrapolated the necessary data to statistically evaluate the probabilities of any future earthquake occurring, according to intensity classes.

scholarly journals Simulation of macroseismic field in Central Greece

1996 ◽  
Vol 39 (5) ◽  
Author(s):  
V. Kouskouna ◽  
S. Chailas ◽  
K. C. Makropoulos ◽  
D. Michalopoulou ◽  
J. Drakopoulos
Keyword(s):  
Soil Structure ◽  
Sedimentary Basins ◽  
Seismic Intensity ◽  
Fault Plane Solutions ◽  
Central Greece ◽  
Geological Conditions ◽  
Macroseismic Intensities ◽  
Tectonic Features ◽  
Epicentral Intensity ◽  
Attenuation Laws

The distribution of seismic intensity is generally influenced by major geological and tectonic features and, on a smaller scale, by local geological conditions, such as the type of surface soil, the surface-to-bedrock soil structure in sedimentary basins and the depth of the saturated zone, The present paper attempted to determine the distribution of macroseismic intensities based on published attenuation laws in the area of Central Greece, using the epicentral intensity, magnitude, length and direction of fault and a considerable number of observation sites, for which the above mentioned information is available, The expected intensity values were then compared to those observed in the same sites, from four earthquakes in Volos, Central Greece, for which the fault plane solutions are also known. The deviations of the observed values from the theoretical model were then related to the local geological conditions and the corresponding correction factor determined for each site.

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