High-resolution seismic reflection profiling across the Shiraiwa fault, eastern margin of the Yokote basin fault zone, northeast Japan : data acquisition and processing

Abstract

The eastern margin of the Yokote basin fault zone extends about 56km at the western foot of the Ou Backbone Range, northeast Japan. The Rikuu earthquake (M=7.2) occurred in the Ou Backbone Range (Mahiru Range) on 31st August, 1896. Associated with this earthquake, four thrust faults-Obonai, Shiraiwa, Ota, and Senya fault3 appeared on the surface of the western foot of the Mahiru Range. These faults were highly sinuous with numerous gaps and en echelon steps. We conducted a high-resolution seismic reflection profiling survey across the Shiraiwa fault. The obtained seismic reflection data were processed by conventional common mid-point methods, post-stack migration, and depth conversion. The subsurface structure across the Shraiwa fault is characterized by branched low-angle reverse faults and conjugate back-thrust. The emergent thrust associated with the 1896 earthquake is regarded to be a subsidiary reverse fault