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

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IGPP
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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


    Phase    LOS    LOS-Zoom



    ALOS-2 ScanSAR Track 140: 2016/04/01 - 2016/04/29



    Phase    LOS    LOS-Zoom



 
   ALOS-2 StripMode Track 34: 2016/02/07 - 2016/05/01 (SM2 - SM3)



  
Phase    LOS
 


   Sentinel-1A TOPS mode Track 18: 2016/03/29 - 2016/04/22


    Phase    LOS



Satellites Track
Mode
Reference Date
Product
Repeat Date
Product
Phase
kmz
LOS
kmz
LOS Data
Sentinel-1A
T040
TOPS
APR 12 2016
s1a-iw1-slc-vv-20160412t110006-20160412t110034
s1a-iw1-slc-vv-20160412t110033-20160412t110101
APR 24 2016
s1a-iw1-slc-vv-20160424t110003-20160424t110028
s1a-iw1-slc-vv-20160424t110028-20160424t110053
s1a-iw1-slc-vv-20160424t110053-20160424t110118
jpg
kmz
jpg
kmz
data_detrended
Sentinel-1A
T018
TOPS
Mar 29 2016
s1a-iw1-slc-vv-20160329t233643-20160329t233708
s1a-iw1-slc-vv-20160329t233708-20160329t233730
APR 22 2016
s1a-iw1-slc-vv-20160422t233644-20160422t233709
s1a-iw1-slc-vv-20160422t233709-20160422t233731
jpg
kmz
jpg
kmz
data_detrended
ALOS-2
T140
ScanSAR
APR 01 2016
IMG-HH-ALOS2100333600-160401
IMG-HH-ALOS2100333650-160401
APR 29 2016
IMG-HH-ALOS2104473600-160429
IMG-HH-ALOS2104473650-160429
jpg
kmz
jpg
kmz
data  detrended
ALOS-2
T034
FEB 07 2016
IMG-HH-ALOS2092277180-160207
IMG-HH-ALOS2092277190-160207
May 01 2016
IMG-HH-ALOS2104697180-160501
IMG-HH-ALOS2104697190-160501
jpg
kmz
jpg
kmz

data_detrended

GMT format grid files

Acknowledgements:  We thank ESA and JAXA for the rapid acquisition and distribution of their data. The ALOS-2 data were provided under PI investigation 1148 - Geometric and Interferometric CALVAL of ALOS-2 PALSAR. The development of the GMTSAR software, specially the processing chain for Sentinel-1A and pre-processor for ALOS-2 was supported by ConocoPhillips and the National Science Foundation through the Geoinformatics program (EAR-1347204) and the GeoEarthScope program (EAR-1147435).