Characteristics of deformation structure around the 2007 Niigata-ken Chuetsu-oki earthquake detected by multi-channel seismic reflection imaging

Abstract

A multi-channel seismic reflection (MCS) survey was conducted to investigate the tectonic structure off Niigata, which caused the 2007 Niigata-ken Chuetsu-oki earthquake, using the research vessel (R/V) KAIREI of the Japan Agency for Marine-Earth Science and Technology. Based on the results of data processing and interpretation of available data, three areas are identified according to seismic characteristics. The most deformed area is located on the continental shelf near the source region of the 2007 Niigata-ken Chuetsu-oki earthquake, i.e., the area east of the Yoneyama-Ogi Uplifts. A remarkable growth of folds, including fault-related folds, and a strong reflector dipping east is identifiable by localized strain concentrations. The second area is located between the Yoneyama-Ogi Uplifts and the Jouetsu Knoll in the Toyama Trough. Although the deformation of deposits in the second area was smaller than in the first area, folds are identified. The third area is located toward the west of the Jouetsu Knoll in the Toyama Trough. No significant deformed structures developed in this area. Based on the interpretation of stratigraphy obtained in previous studies, seismic characteristics, and well data, the development of an anticline was initiated by a compression field after about 3.6 Ma. In particular, the deformation of sedimentary layers by the compression field occurred rapidly after about 1.3 Ma. Folds have grown larger toward the east after about 1.3 Ma. In addition, subsidence of about 0.2 s in sedimentary layers can be seen at the western margin of the Yoneyama-Ogi Uplifts, suggesting that tectonic movement related to reverse faulting has advanced there very recently. From aftershock distribution on a depth section on line S-2 near the hypocentral region, most hypocenters were determined to be below the strong reflector. This result suggests that fold growth has accompanied past large earthquakes, such as the 2007 Niigata-ken Chuetsu-oki earthquake.

Seismic velocity structure along the Sea of Japan with large events derived from seismic tomography for whole Japanese Islands including reflection survey data and NIED MOWLAS Hi-net and S-net data

“…Japan from 2007 to 2011 (Fig. 2) under "Multidisciplinary research project for construction of fault model in the high strain rate zone" and from 2014 to 2020 under "Research project for earthquake and tsunami in the Sea of Japan" by Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan (Shinohara et al 2008;No et al 2009No et al , 2014. In this study, we used the traverse lines near Sado Island and offshore Yamagata prefecture since the traverse lines are surrounded with inland stations and near the source regions of the 2007 offshore Chuetsu Earthquake and the 2019 offshore Yamagata earthquake.…”

“…The grid interval in the vertical direction is described in Table . 1. The resolution for the horizontal direction is 0.2° (approximately 20 km), twice of grid interval (0.1°, 10 km), and (Shinohara et al 2008;No et al 2009No et al , 2014 Origin time that for the vertical direction is also twice the grid interval.…”

“…22). JAMSTEC conducted the reflection survey (No et al 2009) and Nakahigashi et al (2012) estimated the seismic velocity structure with refraction seismology. Their result shows a low-Vp zone less than 3.0 km/s at depths shallower than 3 km and high-Vp between 7.0 and 7.2 km/s at depths of 13-24 km.…”

“…Fig.2Survey lines of reflection seismology by JAMSTEC(Shinohara et al 2008;No et al 2009No et al , 2014 …”

Red relief image map and integration of topographic data in and around the Japan Sea

“…Index map about the range and the classification of data integration. (No et al, 2009) in the Toyama Trough using Schlumberger's Petrel. White points show epicenter distribution (JMA, 2015).…”