Testing the Macroseismic Intensity Attenuation Laws for Vrancea Intermediate Depth Earthquakes

Abstract

The Vrancea seismic region, located at the bending area of the South–Eastern Carpathians in Romania, is the most active zone of seismicity in Europe, producing earthquakes at intermediate depths (60–200 km). The major events (magnitude above 7) are generated at intermediate depth and produce specific patterns of damage over extended areas. In this study we test the macroseismic intensity attenuation laws, using the intensity data point (IDPs) for 8 intermediate depth earthquakes that occurred in Vrancea (between 1738 and 2000). The macroseismic attenuation laws used for testing were Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007), Sorensen et al. (Soil Dyn Earthq Eng, 2010), Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015). The main purpose of the testing is to determine the best attenuation law that will be used to estimate the expected macroseismic intensity at different sites, and to further use them in the assessment of the seismic hazard and risk of the country and to design the real time shake maps. In conclusion, we have decided that Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007) is the best intensity attenuation law for earthquakes located around 90 km depth (the events from March 4, 1977 and May 30, 1990), Sorensen et al. (Soil Dyn Earthq Eng, 2010) law is the best for modelling the macroseismic field due to earthquakes from the lower segment, located around 130 km depth (events from November 10, 1940 and August 30, 1986). For epicentral distances larger than 300 km, Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015) law fits best the intensity distribution.