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The 2018 Hokkaido Eastern Iburi Earthquake: Fault Model(preliminary)

Released: Sep. 12, 2018, updated: Oct. 12, 2018, Japanese version of this page

Summary

An earthquake (Mj6.7) struck eastern Iburi subprefecture in Hokkaido in Japan on September 6, 2018. A fault model was constructed from the crustal deformation data observed by InSAR (ALOS-2) and GNSS.
 
1) The estimated rectangular fault model with a uniform slip shows a high-angle reverse fault motion with the strike of N – S direction.
2) The upper edge of the fault is at a depth of ~16 km.
3) The moment magnitude (Mw) is estimated to be 6.56 (seismic moment: 8.68 × 1018 Nm).

 

Rectangular Fault Model

Fig.1 Observed and model-calculated coseismic displacements by GNSS data (red: observation / blue: calculation). (a) Horizontal component. (b) Vertical component. Star and gray dots indicate the epicenter of the main shock and the aftershock, respectively. The frame indicate surface projections of the fault plane and the thick line represents the upper edge. Red lines on the map stand for active faults.[PNG: 205KB]



Fig.2 InSAR-derived LOS displacement field. Observation (Left). Model Calculation (Middle). Residual (Right).[PNG: 2.4MB]

Table.1 Fault parameters for the fault model

Lon.
[deg]
Lat.
[deg]
Depth
[km]
Length
[km]
width
[km]
Strike
[deg]
Dip
[deg]
Rake
[deg]
Slip
[m]
Mw
141.976
(0.021)
42.586
(0.017)
16.2
(1.7)
14.0
(3.9)
15.9
(3.5)
358
(3.5)
74
(4.4)
113
(7.2)
1.3
(0.4)
6.56



Fig.3 Schematic view of the 2018 Hokkaido eastern Iburi earthquake.[PNG: 1.1MB]


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

The 2018 Hokkaido Eastern Iburi Earthquake

Date-Time September 6, 2018, 03:07(local time)
September 5, 2018, 18:07(UTC)
Hypocenter
Location
42.690°N、142.007°E、Depth:37 km
(JMA, as of September 12, 2018)
Magnitude Mj=6.7(JMA, as of September 12, 2018)
  

Satellite

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

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Contact

YARAI Hiroshi : Head of Division
KOBAYASHI Tomokazu : Chief Researcher
YAMADA Shinya : Researcher
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