Magnitude 5.3 Vrancea April 25,2009

An earthquake of magnitude 5.3 (Richter scale) was produced in the Vrancea region at 100 km depth on April 25, 2009 at 20:18:48 (local time). The earthquake was felt in the epicentral area with intensity V and with intensity III-IV in Bucharest area. It was felt also over a large area extended to NE (Iasi and Kisinew) and SW (Pitesti, Craiova and even Bulgaria).  

            The frequency-magnitude distribution typical for the Vrancea seismic source indicates an average return period for the events of magnitude greater than 5 of 2-3 years. For example, in the last 10 years the following earthquakes with magnitude over 5 were reported:

1999/04/28 08:47 h = 151 km, M = 5.3

2000/04/06 00:10 h = 143 km, M = 5.0

2004/10/27 21:47 h =  99 km, M = 6.0

2005/05/14 01:53 h = 148 km, M = 5.1

            Usually, the aftershock activity following the Vrancea intermediate-depth shocks is significantly less important (as number and size of aftershocks) as compared with similar shocks generated in the crust. Therefore, for the event of April 25 the probability of occurrence of an aftershock which can be felt is extremely low.  

            The focal mechanism determined using P-wave polarities is well constrained indicating a reverse faulting which is typical for the Vrancea intermediate-depth earthquakes with the principal axis of tension (T axis) close to vertical and principal axis of compression (P axis) close to horizontal, oriented SE-NW (see figure 1), while the fault plane is oriented NE-SW.

Figure 1

Event Map