Aftershock sequence of 22 September 2016, Manica-Zinave earthquake (Mw5.6),Mozambique

Abstract

The occurrence of the September 22, 2016 Manica-Zinave earthquake (Mw5.6) and its subsequent aftershocks provided data to study the physics of earthquakes along the southern end of the East African Rift System (EARS). The event occurred in the southern part of Mozambique, less than 40 km from the epicentre of the Mw7.0 Machaze earthquake, which occurred on February 22, 2006. About 320 aftershocks were recorded within a period of 6 months. The analysis of the Manica-Zinave event and its aftershocks was done to understand the tectonics of the region. The aftershocks were relocated using the double difference method. The focal mechanism for this event shows normal faulting, which is consistent with most events along the EARS. Statistical analysis of the aftershock sequence was performed for the calculation of the b-value and the aftershock decay rate p-value. The b-value and p-value obtained for this sequence are 1.02 and 0.86 respectively. These values are typical of aftershock sequences of heterogeneous stressed regions. Due to its proximity, the event might be an aftershock of the Machaze earthquake, which might have occurred due to stress readjustment within the area. The p-value obtained from the Omori law computation suggests that the region is highly stressed.