Calibration and Validation of MEEP Method for Location and Magnitude Estimation of Historical Earthquakes from Intra-Carpathian Region of Romania

Abstract

Intra-Carpathian Region of Romania experienced strong earthquakes as it is mentioned in the national and international databases, e.g. November 26, 1829 (Ms = 6.4), October 10, 1834 (Ms = 6.3), January 26, 1916 (Ms = 6.4), July 12, 1991 (Mw = 5.7). The paper focuses on calibration and validation of MEEP method (Macroseismic Estimation of Earthquake Parameters, Musson & Jimenez, 2008) to provide a homogeneous and repeatable procedure for processing intensity data points (IDPs) which may supply the location and magnitude Mw of historical earthquakes occurred in the Intra-Carpathian Region of Romania and surroundings. The MEEP method is based on 1) grid-search technique for locating the epicentres and 2) the felt area approach to estimate the magnitude. It has the advantage to be used for small and moderate events. We used two high-quality datasets of earthquakes of the 20th century for which macroseismic data points (IDPs), instrumental moment magnitude (Mw) and instrumental epicentral coordinates are available, one for calibration and the other one for validation of the method. The main parameters used through MEEP algorithm were calibrated at regional scale using high-quality instrumental data: 1) crustal attenuation Q3 = 435 (Q at f = 3 Hz, which is understood to be the limit of the human perception of seismic waves), 2) Kövesligethy’s inelastic attenuation (∝ = 0.0065), 3) isoseismic spacing coefficient (k = 3.1) and 4) C = 2015, a constant generally related to tectonic regime. The MEEP method was successfully tested for events occurred within extra-Carpathian regions and the Pannonian Basin.