Ground Shear Strain and Rate of Erosion in The Coastal Area of North Bengkulu, Indonesia Muhammad Farid 1,a , Kirbani Sri Brotopuspito 2,b , Wahyudi 2,c , Sunarto 3,d , Wiwit Suryanto 2,e 1 Departement of Physics, Mathematical and Natural Science Faculty, Bengkulu University 2 Laboratory of Geophysics, Mathematical and Natural Science Faculty, Gadjah Mada University 3 Departement of Physics Geographics and Enviromental, Geography Faculty, Gadjah Mada University a moh_farid50@yahoo.com, b kirbani@yahoo.com, c pwayudi2002@yahoo.com , d sunartogeo@gmail.com, e wiwit@gadjahmada.edu, Keywords: Ground Shear Strain, Seismic Vulnerability Index, the rate of erosion, North Bengkulu Districts Abstract. North Bengkulu district has an area prone to earthquakes, because this area is very closed to the Sumatra subduction zone to the Eurasian tectonic plate. Coastal area in this region is experiencing with the very fast erosion. This is thought to have relation with earthquake-prone zones. This study aims to find the relationship between Ground Shear Strain (GSS) and rate of erosion in the coastal area of North Bengkulu. The data of coastal erosion rate was obtained by overlaying shoreline in 1947 and 2012. The GSS can be obtained by multiplying Seismic Vulnerability Index (SVI) and Peak Ground Acceleration (PGA) values around the shoreline. Seismic Vulnerability Index was obtained by processing microseismic data acquired using three component in short period of seismometers. The PGA was obtained from the historical earthquake and calculated by using Fukushima-Tanaka equation. The results show that the value of GSS varies between 0.0001 to 0.0055, and the SVI values is ranging from 1.2 to 16.1. In addition, we estimated that PGA value is 92 to 120 gal and the rate of erosion between 3.6 up to 5.8 m/yr. GSS value for each type of shore is 0.00046 for the shore of fine sandy flat, 0.0043 for shore of muddy flat, 0.0001 for shore of rocky flat, 0.0006 for shore of sandy rugged, 0.0003 for shore of steep lava rocky, 0.0014 for shore of steep rocky clay, 0.0011 for shore of tufa steep sandy stones, and 0.0014 for the shore of steep rocky tuffaceous clay. It is found that the GSS value depends on the type of coastal. In this case, flat coastal muddy show highest effect on the GSS. Both SVI and GSS can be estimated to be a quadratic relation to the erosion rate. INTRODUCTION North Bengkulu district has a coastal length of about 60 km, in the range between 3.2° - 3.6° south latitude, dealing with the Indian Ocean. Erosion occurs almost along the beach with a relatively high pace. Geological conditions which are dominated by Bintunan Formation consist of tuffaceous clay and sandy tufa stone. Both of these rock types eroded quite heavy. In addition to the geological conditions that allow the erosion, vibration condition that often occurs predicted earthquake accelerated the rate of erosion in North Bengkulu shore. Erosion at many points along the coast of North Bengkulu estimated because the value of ground shear strain (GSS) is high. Higher GSS values is possible because the region is in soft soil conditions [1]. The erosion occurs due to the high vulnerability of the coastal ocean dynamics such as the pounding waves, the wind, the destruction of shade trees and ocean currents [2]. Erosion is Advanced Materials Research Vol. 896 (2014) pp 521-524 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.896.521 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 202.43.95.18-07/02/14,08:07:13)