Constraining Early-stage Rifting Through Rapid Response to the Lake Malawi Earthquake Sequence of December 2009

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This RAPID proposal addresses nine earthquakes of magnitude 5 and larger that have taken place in the northern Malawi segment of the East African Rift (EAR) system. These events are extremely rare, and their swarm-like characteristics are highly unusual for this particular region and for the Western Branch of the EAR as a whole. They will deploy a network of 10 seismic stations in the region of these earthquakes to record further main shocks (if they occur) and aftershocks and to relocate these events to better constrain the fault(s) or other subsurface features that are causing them. In particular they will evaluate: (1) whether current events indicate that extension is being accommodated on the major basin-bounding border fault, or whether the extensional strain is occurring primarily on secondary faults in the hanging wall of the major system; and (2) whether deep magmatic activity is associated with the events. These earthquakes offer a rare and important opportunity to address key aspects of deformation and seismogenesis in an early stage rift. Accurate aftershock locations require observations from the epicentral region, where there is currently only one operating seismometer. A rapid deployment is necessary.The December 2009 earthquake sequence has resulted in threecasualties, hundreds of injuries and thousands of displaced people. Aftershocksassociated with the sequence continue, and given the swarm-like character of the dozen or so largest events, it is possible that additional damaging events are still to come. Malawi currently has very limited capacity to monitor and locate these earthquakes; they have no permanent national network, and as of this writing only two seismic stations are in northern Malawi region recording these events.The PIs will work closely with the Geological Survey of Malawi (GSM) in earthquake detection and location techniques, as well as with the USGS, USAID, and the US Embassy to coordinate with the other outreach and humanitarian efforts underway.