The 2017 Iran-Iraq Earthquake: Crustal deformation detected by ALOS-2 data

A large earthquake (Mw 7.3, USGS) occurred near the Iran-Iraq border on November 12, 2017. Serious damage such as building collapse and many deaths (> 500) has been reported around the epicenter. To measure the crustal deformation caused by the earthquake, we applied interferometric analysis using ALOS-2/PALSAR-2 data.

The results obtained from the data are summarized as follows.

[Features of the crustal deformation]

• Large displacement (~90 cm upward and ~50 cm westward) has been detected around 20 km NNW of Sarpol-e Zahab (Figs. 1 and 2).
• Around the epicenter, ~30 cm downward and ~35 cm westward displacement has been detected (Figs. 1 and 2).
• The area with more than 10 cm displacement extends ~80 km in diameter (Figs. 1 and 2).
• The detected deformation pattern implies that reverse slip on a low dip angle fault plane with the strike of NNW-SSE direction occurred (Fig. 7). This mechanism is consistent with the one estimated from seismic waves.
• Apart from the deformation associated with the fault slip, lots of localized displacements have been detected at mountain slopes, and might have been triggered by the seismic motion (Figs. 4bc and 5bc).

[Fault model]

• We constructed a fault model (slip distribution) from the crustal deformation measured by InSAR (Fig. 7).
• The estimated slip centered at the south of epicenter, and reached 3 m.
• The estimated moment magnitude (Mw) is 7.36 (seismic moment 1.4 x 10²⁰ Nm).

 

2.5-D analysis
Two or more line-of-sight displacements with different observing directions (Figs. 4 and 5) can be decomposed to quasi up-down and east-west components.

Fig. 3. Geometry of 2.5-D analysis

Fig. 5. [PNG:6.06MB]
 

Fig. #	Date	Time (UTC)	Flight Dir.	Beam Dir.	Obs. Mode *1	Incidence Angle (Epicenter)	Bperp	KMZ
4	2016-08-09 2017-11-14	20:59	Asc.	Right	W-W	47°	-70 m	(a)8.24MB (b, c)2.33MB
5	2017-10-04 2017-11-15	08:49	Des.	Right	W-W	47°	+160 m	(a)4.37MB (b, c)1.42MB

*1 W：ScanSAR (Normal)
(cf. ALOS-2 Project / PALSAR-2 (JAXA))


Fig. 6. Area of interest

Analysis by GSI from ALOS-2 raw data of JAXA.
These results were obtained through the activity of the SAR analysis working group of the Coordinating Committee for Earthquake Prediction.

Fig. 7. Constructed fault model [PNG: 867KB]

Date-Time	November 12, 2017, 18:18 (UTC)
Hypocenter Location	34.905°N, 45.956°E, Depth: 19.0 km (USGS, as of November 15, 2017)
Magnitude	Mw=7.3 (USGS, as of November 15, 2017)

ALOS-2 (Advanced Land Observing Satellite 2) launched by Japan Aerospace Exploration Agency on May 24, 2014

Kobayashi, T., Y. Morishita, H. Yarai, and S. Fujiwara (2018), InSAR-derived Crustal Deformation and Reverse Fault Motion of the 2017 Iran-Iraq Earthquake in the Northwest of the Zagros Orogenic Belt, Bull. Geospatial Info. Auth., 66. [PDF: 1.3MB]

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YARAI Hiroshi : Head of Division
KOBAYASHI Tomokazu : Chief Researcher
MORISHITA Yu : Chief Researcher