Abstract
The goal of this paper is to develop a new empirical relationship between observed macroseismic intensity and strong ground motion parameters such as peak ground acceleration (PGA) and velocity (PGV) for the Vrancea subcrustal earthquakes. The recent subcrustal earthquakes provide valuable data to examine these relationships for Vrancea seismogenic region. This region is one of the most active seismic zones in Europe and it is well-known for the strong subcrustal earthquakes. We examine the correlation between the strong ground-motion records and the observed intensities for major and moderate earthquakes with Mw ≥ 5.4 and epicentral intensity in the range VI to IX MSK degrees that occurred in Vrancea zone in the period 1977-2009. The empirical relationships between maximum intensity and ground parameters obtained and published by various authors have shown that these parameters do not always show a one-to-one correspondence, and the errors associated with the intensity estimation from PGA/PGV are sometimes +/-2 MSK degree. In the present study, the relation between macroseismic intensity and PGA/PGV will be given both as a mathematical equation, but also as corresponding ground motion intervals. Because of the intensity data spreading and errors related to mathematical approximations, it is necessary to systematically monitor not only the acceleration and velocity but also all the other ground motion parameters. The mathematical relation between these parameters might be used for the rapid assessment of ground shaking severity and potential damages in the areas affected by the Vrancea earthquakes.
Highlights
The past bad experience from the last decades caused by worldwide natural disasters, especially those associated with major earthquakes which has determined defensive measures from the international communities
Since the macroseismic intensity value is not directly associated with peak ground acceleration (PGA) and PGV values, which are obtained from one point, relationships were obtained by regression between the MI and geometric mean of PGA and PGV for each intensity level
In this study we opted for an orthogonal regression which allows for uncertainty on both variables (i.e., MI and PGM), and produces reversible relationships
Summary
The past bad experience from the last decades caused by worldwide natural disasters, especially those associated with major earthquakes which has determined defensive measures from the international communities. Empirical relationships between macroseismic intensity and ground motion parameters are one of the evident applications used to obtain intensities directly from recorded data or to estimate PGA and PGV data for historical earthquakes and , in sites where macroseismic information are available Another major use of such relationships is represented by the Shake map application
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