Mw 7.8 Ecuador Earthquake: Line of sight displacement and the down-dip rupture revealed by ALOS-2 and Sentinel-1A  Interferometry

Xiaohua Xu and David Sandwell



Institute for Geophysics and Planetary Physics
University of California, San Diego, USA

Paper in prep.

The Mw 7.8 Ecuador earthquake occurred on April 16, 2016 close to the shoreline of north Ecuador. The background tectonics shows a converging boundary between the young Nazca plate and the Pacific plate (~61mm/yr USGS report). By the time the earthquake struck, we are lucky to have a few on-board satellites that acquired a wealth of InSAR acquisitions. The C-band Sentinel-1A satellite, operated by the European Space Agency (ESA), even though severely affected by the thick ground vegetation, managed to provide a 12-day coverage for the descending track 40 and a 24-day coverage for the ascending track 18. The data are available on the Sentinel Datahub. The L-band ALOS-2 satellite, operated by the Japanese Aerospace Exploration Agency (JAXA), collected ScanSAR data for track 140 and the data can be found on the ALOS-2 User Interface Gateway.

This page is to provide the extracted line-of-sight deformation data from these 2 satellites and construct a elastic model to reveal the down-dip of the rupture for this subduction zone earthquake. We'll keep presenting images for each track and update the line-of-sight data once they are available. We'll also include KMZ files for Google Earth. The InSAR data are processed with an open source software GMT5SAR and post processing are done with GMT and Matlab. The InSAR phase are filtered with a 400m Gaussian filter. The line-of-sight data are acquired by merging different swaths' phase and then unwrapping using snaphu. Then they are deramped with excluding the main shock area in order to account for orbit error and ionospheric effect.

The line-of-sight (LOS) data also include a look vector pointing from the point on the ground to the position of the satellite. The data represent a block median average of the LOS in 0.01 degree bins.  The format is:


 lon                lat             topo (m)        east          north        up               los(mm)          sig(dummy)
-78.736111  1.696111  8.9197050  0.582252  -0.122148  0.803780   -47.4433994293  -1
-78.728333 1.696111  13.485863  0.581515  -0.122007   0.804335  -50.0596561432   -1
-78.721111  1.695000  10.788337 0.580808  -0.121845   0.804870  -16.398068428     -1
-78.997222 1.689444  -0.494510  0.606106  -0.127184   0.785150  -51.4392814636   -1
-78.989444 1.689444  -0.454794  0.605402  -0.127086  0.785709   -53.6953849792   -1


   Sentinel-1A TOPS mode Track 40 : 2016/04/12 - 2016/04/24