Ground displacement caused by natural earthquakes, determining based on differential interferometry SAR and multiple aperture interferometry techniques

Abstract

Annually, several hundred natural, strong earthquakes are recorded on the Earth. Not all of them cause ground displacement. Displacement depends on the location of the epicenter of an earthquake, its character, as well as geological and geophysical conditions. Satellite radar interferometry (InSAR) is a measurement technique used to observe displacements of the terrain surface, which is able to identify even small displacements, over a very large area. Therefore, it is a good tool to study land displacements caused by seismic shocks. Currently, new images are available every few days, so almost continuous observations are possible. The article presents two different techniques for processing two Synthetic Aperture Radar (SAR) images. The first, Differential Interferometers SAR (DInSAR), allows to determine pseudo-vertical displacements - in the direction of the line of sight (LOS). The second, Multiple Aperture Interferometry (MAI), allows determination of displacements in the horizontal plane, consistent with the along - track. The calculations were carried out for earthquakes that occurred off the west coast of North America. The Baja earthquake, 7.2 magnitude, occurred on 04 April 2010 in Baja California state (Mexico). The use of two techniques (DInSAR and MAI) allows to observe displacements caused by natural tectonic activity in more than one direction, therefore the measurement is more comprehensive.