Nepal Earthquake: Line of Sight Deformation from ALOS-2 Interferometry
Eric
Lindsey 1, Ryo Natsuaki 2,
Xiaohua Xu 1, Masanobu Shimada 2,
Manabu, Hashimoto 3, and David Sandwell
1
May 7, 2015
Lindsey, E. O., R. Natsuaki, X. Xu, M. Shimada, H. Hashimoto, D. Melgar, and D. T. Sandwell, Line of Sight Deformation from ALOS-2 Interferometry: Mw 7.8 Gorkha Earthquake and Mw 7.3 Aftershock, Geophysical Research Letters, 42, doi:10.1002/2015GL065385, 2015 (pdf).
The Mw 7.8 Gorkha earthquake struck on April 25, 2015 in a region with less than optimal seismic and geodetic coverage. Fortunately two InSAR satellites were operational before the earthquake and continue to collect measurements of line-of-sight (LOS) deformation. The Sentinel-1a satellite, operated by the European Space Agency (ESA), has collected a wealth of C-band InSAR data and the results are available on the INSARAP PROJECT page. The ALOS-2 satellite, operated by the Japanese Space Agency (JAXA), has collected a wealth of L-band InSAR data and results are published at the JAXA site. This page is
focused on the extraction of line-of-sight deformation
data from the ALOS-2 satellite. The original
SAR data were obtained from the AUIG User
Interface Gateway under a calibration and
validation project sponsored by JAXA. We present
images for each track and frame as they become
available. Also
include are KMZ files for Google Earth as well as an
ASCII file of LOS data. Many of the
images are collected in the ScanSAR mode. Data were
processed with GMTSAR
with additional post processing using GMT. The phase
was unwrapped using the snaphu
software. The
unwrapped phase of individually processed frames and
subswaths were merged by adding visually determined
phase discontinuities of integer multiples of 2 pi. Several of
the ScanSAR data have large phase ramps related to
orbit error and/or ionospheric delays. We remove a
ramp from the composite LOS data but retain the ramp
in the original wrapped phase. The line-of-sight (LOS) data also include a unit 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(mm) |
 |
 Update: a Mw
7.3 aftershock occurred on May 12, 2015 at the eastern
end of the rupture. ALOS-2 observations and preliminary
modeling suggest that this event occurred on a part of
the fault that was highly stressed by the April 25
mainshock.
The sum of the displacement from the Mw7.8 and Mw7.3
earthquakes is shown on the right. There is a
small patch between the two rupture zones that has not
slipped yet. The moment magnitude potential of
this patch is ~Mw6.9. kmz |
 |
| Track Mode |
Reference Date Product |
Repeat Date Product |
Phase kmz |
LOS kmz |
LOS Data |
| T048 ScanSAR |
FEB 22 2015 ALOS2040533050-150222 |
MAY 03 2015 ALOS2050883050-150503 |
jpg kmz |
jpg kmz |
raw data data_detrended |
| T048 ScanSAR |
APR 05 2015 ALOS2046743050-150405 |
MAY 03 2015 ALOS2050883050-150503 |
jpg kmz |
jpg kmz |
data detrended |
| T157 Swath |
FEB 21 2015 ALOS2040460540-150221 |
MAY 02 2105 ALOS2050810540-150502 |
jpg kmz |
jpg kmz |
raw data data detrended |
| T047 ScanSAR |
MAR 31 2015 ALOS2046003050-150331 |
APR 28 2015 ALOS2050143050-150428 |
jpg kmz |
jpg kmz |
data detrended |
| T048 ScanSAR |
MAY 03 2015 ALOS2050883050-150503 |
MAY 17 2015 ALOS2052953050-150517 |
jpg kmz |
jpg kmz |
data detrended |
