FOCAL MECHANISM SOLUTION OF THE 15TH MARCH 2008, NYAMANDLOVU EARTHQUAKE

摘要

The focal mechanism solution of the 15th March 2008 earthquake (mb = 4.3) that occurred in the Nyamandlovu area, northwest of Bulawayo City, Zimbabwe, has been determined from P-wave first motion polarities. Results show normal oblique left lateral faulting. The earthquake mechanism bears a signature that is almost identical to those of events recorded in the Zambezi Branch of the East African Rift Zone. Synthetic seismograms compared with observed data from regional stations were employed for depth determination. This event had a shallow depth of 5 km. Earthquakes in the area tend to occur either after a significant drought or a wet season of considerable length. The area is underlain by thick Karoo sandstones that form an aquifer of high potential water storage. These events are therefore most probably induced by pore - pressure differentials in the underlying rock.