Bulletin of the GSI (Vol.66)
Tomokazu Kobayashi,Yu Morishita,Hiroshi Yarai and Satoshi Fujiwara
An inland earthquake with a moment magnitude of 7.3 occurred in western Iran / eastern Iraq on November 12, 2017. Applying an interferometric SAR (InSAR) analysis using ALOS-2 SAR data to the earthquake, we detected the crustal deformation in the northwestern part of the Zagros orogenic belt. We successfully obtained quasi-up-down and quasi-east-west displacement components by combining two sets of InSAR data. The results show that uplift occurred in the western part of the source region with ~90 cm at most, while in the east subsidence occurred with ~30 cm at most. Most of the source region moved westward with ~50 cm at most. Our preferred fault model shows that the observations can be accounted for by a nearly pure reverse fault motion with a slight dextral motion on a low-angle fault plane dipping northeast.
Takuya NOJIRI, Toru NAGAYAMA, Taro UBUKAWA, Shigeto KAWASAKI and Hiroshi MURAKAMI
Since October 2015, the Geospatial Information Authority of Japan (GSI) has served as the President of the Regional Committee of the United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP) and other important posts (term: 2015 to 2018), including the Chair of a working group. Through these roles, GSI has contributed to the improvement of geospatial information management in the Asia-Pacific region and led discussions on related policies, frameworks and capacity development by sharing information and experience. GSI has also played a coordinating role in proposing priority issues and conveying requests from the Asia-Pacific region to the United Nations Committee of Experts on Global Geospatial Information Management.
In October 2017, GSI hosted the 6th Plenary Meeting of UN-GGIM-AP in Kumamoto City, Kumamoto Prefecture, Japan. On that occasion, GSI led the discussion at a special session entitled “Geospatial Information for Disaster Response - Case Study on the Disaster Response for the Kumamoto Earthquake in April 2016” to share Japan’s experience with participating member countries by introducing GSI’s response to the Kumamoto Earthquake that occurred in the previous year. To facilitate discussions at the special session, GSI prepared a “Case Story” about its response to the 2016 Kumamoto Earthquake and distributed it to UN-GGIM-AP member countries two weeks before the Plenary Meeting. That case story is reported herein as the Appendix.
Toshihiro YAHAGI, Kenji YOSHIDA, Takayuki MIYAZAKI, Yoshifumi HIRAOKA and Basara MIYAHARA
The Geospatial Information Authority of Japan (GSI) has carried out nationwide gravity surveys for about 60 years and provided a national gravity standard network, which has been widely used for various purposes such as calculation of orthometric heights, calibration of weighing instruments and exploration of underground structures. However, the gravity standard network needs to be revised since gravity changes have accumulated due to crustal deformation and it has become possible to measure gravity values more precisely thanks to recent improvements in gravimeters. Therefore, the GSI released an updated gravity network, named the Japan Gravity Standardization Net 2016 (JGSN2016), on 15 March 2017 for the first time in 40 years.
JGSN2016 consists of gravity values at 32 fundamental gravity points and 231 primary gravity points (as of Mar. 2017). Each gravity value was calculated as follows: 1) determining the absolute gravity value of each fundamental gravity point based on absolute gravity measurements, 2) measuring gravitational differences along each baseline by relative gravimeters and 3) calculating the most probable gravity value of each primary gravity point by carrying out the net adjustment calculation using the values determined in 1). In the course of the process, the influences of solid-earth tide, atmospheric pressure, polar motion and ocean tide were adopted after removing outliers by statistical screening. In addition, the most appropriate combination of parameters for the net adjustment was determined by the Bayesian Information Criterion (BIC). The absolute gravimeters were calibrated through the annual comparison campaign with other domestic organizations which have absolute gravimeters. Thanks to these various improvements, JGSN2016 achieved precision of 3 and 11 μGal for the fundamental and primary gravity points, respectively.