Remote sensing techniques in earthquake monitoring
The greater part of Malawi is underlain by crystalline Basement Complex Rocks of Precambrian to lower Paleozoic age; these are referred to as the Malawi Basement Complex (Carter, 1973). The Basement Complex was subjected to a prolonged structural and metamorphic history that was associated with epeirogenic movements, faulting and formation of the Malawi Rift Valley (South Western arm of the East African Rift Valley).В
The Malawi Rift Valley was initiated in the late Tertiary (Crossley and Crow, 1981) and extends for about 800 Km from the Rungwe volcanic region in South Tanzania through Lake Malawi and Shire River into Mozambique. In Malawi, it is largely dominated by a linear trough forming Lake Malawi (Scholz C.A., 1989).
By virtue of its geological position (Along the East African Rift Valley) Malawi is subjected to Earthquakes. Earthquake monitoring in Malawi commenced in 1962 with two observation stations planted in Chileka and Mzuzu. In 1989, the network expanded to four stations (Porta-corders). Now, the observation network has increased to 10 operational broadband stations installed across the country.
В Data from the local catalog and other international sources (ISC, NEIC) indicate that Malawi has experienced moderate earthquakes in its history. The most recent ones being on 10thВ March, 1989 in Salima (Central Region) and the December 19, 2009; in Karonga recording the highest magnitude on the Ritcher Scale. The 2009, Karonga earth quake has been the largest and most destructive so far recorded in this region where lives and property were destroyed.
During the Karonga earthquakes, the Department of Geological Survey (GSD)В В sought assistance from the United States Geological Survey (USGS), Israel Geological Survey (IGS) and Columbia University Lamont Doherty Earth Observation (LDEO) to assist in the monitoring of the December, 2009 aftershocks. The Eastern and Southern Africa Regional Seismological Working Group (ESARSWG) also used geophysical and geological methods within the Karonga earthquake affected area to infer the existence of the Karonga Fault.
Using remote sensingВ IGS managed to locate the Karonga Fault that was as a result of the December, 2009 earthquakes similarly through the application of geophysical techniques, (Seismic methods), the Department of Geological Survey of Malawi mapped out active faults, delineating earthquake prone areas across the country,
From the monitoring of earthquakes and analysis of geophysical and geological data, the Department plays an advisory role to the general public in the country on the dangers of earthquakes as natural hazards. It also provides information about the seismicity of various places in Malawi and technical advice to the construction industry on the type of buildings and other infrastructures to be constructed in specific areas taking into consideration theseismic activeness of that area.
The application of Remote Sensing techniques in earthquake monitoring plays a great role in mapping out of faults which upon application of seismic techniques can be concluded whether the faults are active or not. GSD is still continuing with the application of Remote Sensing in earthquake monitoring across the country.