Investigation of fault-zone induced site effect in the Izmit basin, Turkey


Fırtana Elcömert K. , Kocaoglu A.

ACTA GEOPHYSICA, 2021 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Publication Date: 2021
  • Doi Number: 10.1007/s11600-021-00673-8
  • Title of Journal : ACTA GEOPHYSICA
  • Keywords: Fault-zone induced waves, Site amplification, Seismic wave propagation simulation, Finite difference method, Izmit basin, NORTH ANATOLIAN FAULT, SINGLE-STATION MICROTREMOR, KARADERE-DUZCE BRANCH, SHEAR-WAVE VELOCITY, BAY AREA TURKEY, GUIDED-WAVES, TRAPPED WAVES, GROUND MOTION, SAN-ANDREAS, EARTHQUAKE

Abstract

The seismic hazard in the Izmit basin, located in Marmara region of western Turkey, is high due to the northern branch of the North Anatolian Fault (NAF) and the potential ground motion amplification that may be caused by local site conditions, sedimentary basin effect as well as fault zone (FZ) induced site effect resulting from the generation of guided waves. In this study, we elaborate the relevance of the FZ-induced site effect in the Izmit basin along a 16.5-km-long N-S profile across the basin and perpendicular to the NAF by time and frequency domain analysis of waveforms obtained from two-dimensional (2D) simulations of viscoelastic wave propagation for a double-couple source at 14 km depth using a reference (basin-only) model and three basin-with-fault models: shallow (6 km), intermediate (12 km) and deep (19 km) FZ models. Our results show that the FZ-induced site effect within and near the northern branch of NAF in the Izmit basin can be very prominent with amplifications of about 5-10 in the frequency range of 0.05-4 Hz and about 20 at frequencies above 2 Hz, respectively. We obtain the most dramatic results for the deep FZ model causing shear- and surface-wave amplifications of about 15 at frequencies higher than 2.5 Hz for the distances between 6 and 13 km.