SENTINEL-1 INSAR OBSERVATIONS OF GROUND DEFORMATION IN THE EARLY-STAGE NORTHERN NYASA RIFT

The SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) multidisciplinary research project is focused on understanding the dynamics of early-stage rifting. An important objective of the project is to quantify surface deformation associated with active tectonic processes: Including strain rates from active extension, co-seismic displacements due to crustal faulting, and uplift due to magmatic intrusions. Since 2012, the project has deployed several geophysical monitoring networks, including GPS and seismic stations spanning a 500km region. Geodetic ground stations have been augmented by regular ESA Sentinel SAR imagery acquisitions since 10/2014, but InSAR measurements of ground motion are encumbered by atmospheric noise. We have processed hundreds of interferograms through 06/2017 in order to mitigate atmospheric signals and provide a synoptic view of average surface motions in the region. InSAR observations have proven especially useful in constraining fault models of shallow crustal earthquakes. For example, global moment tensor catalog epicentral locations for a Mw5.1 earthquake occurring on 12/31/2014 near Karonga, Malawi differ by over 20km. Geodetic models of normal faulting, based on a moment tensor solution using data from the SEGMeNT seismic array, are consistent with 3 cm of subsidence located 10km from the nearest global catalog epicenter. We also report on the InSAR observations within 20 km of each SEGMeNT GPS station and compare the results with GPS time series. In addition, we will discuss the lack of observed surface displacements of magmatic origin at the Holocene Rungwe Volcanic complex.