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 three casualties, hundreds of injuries and thousands of displaced people. Aftershocks associated 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.
Intellectual Merit. On December 6, 2009, an unusual sequence of earthquakes began in the Karonga region in northern Malawi (Figure 1). Malawi, a landlocked, agrarian country, is located on the East African Rift—a giant, slowly opening crack that continues 2,400 miles across Africa. The rift has produced major quakes throughout East Africa. However, northern Malawi had been calm for decades, so the earthquakes caught everyone by surprise. The sequence began with an event of Richter Magnitude (Mw) 5.8, and was punctuated 12 days later with an Mw 6.0 event. It resulted in four casualties, 300 injuries and thousands of displaced people. In addition to the humanitarian impact, the earthquakes are important scientifically– the complex sequence of events provides a rare opportunity to better understand how rift-zone faults operate. At the time, Malawi had just two seismic stations, insufficient for monitoring the subsequent aftershocks and associated danger. The Malawi Geological Survey Department (MGSD) requested assistance to monitor the ongoing earthquake sequence, and we responded with a temporary deployment of seismic stations. We obtained three seismic stations from the US seismological consortium IRIS (www.iris.edu), which maintains a small fleet of instruments specifically for rapid aftershock deployments. We borrowed two additional stations from Prof. Cindy Ebinger (Univ. of Rochester). Funding to travel to Malawi and deploy the instruments was provided by Columbia University’s Lamont-Doherty Earth Observatory and the Earth Institute, and we secured NSF RAPID funding (this grant) to return to Malawi to recover the data and instruments. Between Jan 1 and Jan 15, 2010, we deployed six broadband stations in the Karonga region of northern Malawi to monitor aftershocks of the December sequence. In early May, we returned to Malawi to retrieve both the data and the instruments. We recorded thousands of aftershocks, and the analyses of these data are ongoing under separate funding. The seismic data have been archived at the IRIS Data Management Center (www.iris.edu/dms/dmc), and they are openly available to the community. Broader Impacts. This project had an immediate, wide-ranging impact on local population. We worked side-by-side with personnel from the MGSD, providing them with extensive training in seismic equipment and field methods (Figure 2). This effort directly resulted in the purchase of equipment by the MGSD for 9 stations to begin a seismic network in Malawi, which is now operational. We directly interacted with a large number of local teachers, police officers, and villagers, explaining the earthquakes to them, and providing advice on earthquake response. We conducted television and radio interviews about earthquakes and the necessity of seismic monitoring, which were widely replayed around the country. Products resulting from this project: We published a blog documenting the field deployment and associated issues related to providing rapid technical assistance following a seismic disaster: http://blogs.ei.columbia.edu/blog/tag/east-africa-rift/ Seismic data collected during the experiment is available at: www.iris.edu/dms/dmc/
