Crustal Deformations Moved Wajima 2 Meters Southwest After Quake; Authorities to Resurvey Control Points on Noto Peninsula

The Yomiuri Shimbun
Source: Geospatial Information Authority of Japan

The city of Wajima, Ishikawa Prefecture, shifted a maximum of two meters southwest due to crustal deformations caused by the massive earthquake on New Year’s Day, according to analysis by the Geospatial Information Authority of Japan.

The authority also confirmed shifts of about 90 centimeters in both the city of Suzu and the town of Anamizu.

Many control points, which are used as the basis for creating maps, on the Noto Peninsula are believed to have been affected by crustal deformations caused by the Jan. 1 earthquake. The authority therefore plans to resurvey control points on the peninsula.

Officials analyzed location data from both pre- and post-quake observations, using the global positioning system among other methods.

They were initially unable to obtain certain data due to the deteriorated telecommunications environment, but managed to add missing data by Sunday and recalculated.

The largest crustal deformation was observed at a location near the coast in the eastern part of Wajima. The data from the location initially was not delivered to the authority, but the later additional data also showed a 1.3-meter uplift at the same location.

When the authority released its analysis on Jan. 2, an about 1.2-meter westward movement at a different location near central Wajima city was thought to be the maximum.

The latest analysis also confirmed the following crustal deformations:

*Suzu: About 90-centimeter shift to southwest, about 90-centimeter uplift

*Anamizu: About 90-centimeter shift to northwest, about 3-centimeter uplift

*Noto Island: About 70-centimeter shift to north, about 30-centimeter subsidence

Given the large scale of crustal deformations, the authority plans to resurvey control points in the Noto Peninsula.

A maximum shift of more than five meters was observed after the 2011 Great East Japan Earthquake. This prompted the authority to resurvey the so-called triangulation points, which represent the basis for longitude and latitude, at about 1,800 control points in the area.