Time lapse seismic analysis of the Tohoku-Oki 2011 earthquake

M Landrø,S Kodaira,T Fujiwara,T No,W Weibull,B Arntsen

doi:10.1016/j.ijggc.2019.01.002

Abstract

A detailed time lapse seismic analysis of subsurface movements is presented using seismic 2D lines acquired prior to and after the Tohoku-Oki earthquake offshore Japan in 2011. Estimated movements of the seabed from the time lapse seismic data corresponds well with estimations using bathymetric data. On the shelf, we find seabed subsidence of up to 8–9 m, and closer to the Japan trench, we find a seabed uplift of more than 10 m. Along the 100 km long 2D seismic line, we find alternating subsidence and uplift. We find horizontal displacements at the seabed that are significantly larger, up to 40–50 m, however these estimates are more uncertain. Close to the Japan trench, these horizontal displacements are practically opposite in direction (pointing towards the trench from both sides) and large (˜15 m). At the sediment-basement interface, we estimate vertical subsidence of two independent large blocks (each 4 km wide) to be up to 14 m. This means that the sediment package in this region has been stretched by 5–6 m. This type of overburden stretching is similar to hydrocarbon reservoirs that compact due to production and produce corresponding overburden stretching. Several examples of new faults, new layering and orientation of sedimentary layers are found. Implications for subsurface storage of CO2 in areas close to subduction zones are also discussed.

Highlights

Co-seismic fault slip behaviour of the 2011 Tohoku-Oki earthquake has been intensively studied by seismological, geophysical, geological, geodetic and tsunami wave data
Various models of co-seismic slip distributions (e.g., Fujii et al, 2011; Lay et al, 2011; Ide et al, 2011; Satake et al, 2013) have been suggested, there is a general consensus that a large co-seismic fault slip of more than 50 m reached the trench axis of the central part of the Japan Trench
The main objective of this paper is to investigate if a detailed, quantitative time lapse seismic analysis of two datasets acquired before and after the earthquake, can reveal new insight into rock movements and changes in rock properties

Summary

Introduction

Co-seismic fault slip behaviour of the 2011 Tohoku-Oki earthquake has been intensively studied by seismological, geophysical, geological, geodetic and tsunami wave data. Various models of co-seismic slip distributions (e.g., Fujii et al, 2011; Lay et al, 2011; Ide et al, 2011; Satake et al, 2013) have been suggested, there is a general consensus that a large co-seismic fault slip of more than 50 m reached the trench axis of the central part of the Japan Trench This large co-seismic slip generates a large seafloor displacement (Sato et al, 2011; Kido et al, 2011; Ito et al, 2011) which is considered to be the major cause of the large tsunami wave hitting the coastline of the eastern part of Japan. Some of these challenges include variations in acquisition set up and positioning issues causing lower repeatability compared to conventional time lapse seismic surveys

Objectives

Results

Discussion

Conclusion