Landslide Potential Analysis Using Microtremor Data on the Main Route to Beach Tourism in Tanjung Pandan, Pesawaran, Lampung

Abstract

Tanjung Pandan has much beach tourism which attracts many tourists. However, the only road access to these tourist destinations is bordered by hills and cliffs on either side. Its condition has a potential to landslides. This study aims to determine the landslides potential caused by earthquakes considered as external force by obtaining the ground shear strain (GSS) value and obtaining the depth of the slip surface at the measurement location. There are 10 measurement points in two different locations. The method used is the horizontal to vertical spectral ratio (HVSR) method to obtain the value of the dominant frequency and the amplification factor. These two parameters are then used to obtain the value of peak ground acceleration (PGA) and GSS. The depth of the slip surface is obtained by the ellipticity curve inversion method. The frequency natural values vary from 1.4 to 8.2 Hz and the amplification factor values vary from 2.4 to 5.2. The PGA values obtained from Fukushima-Tanaka equation have range from 3.02 to 3.04 gal using the 6.6 Mw Liwa earthquakes considered as the reference earthquake. The GSS values vary from 3.5x10-6 to 3.2x10-5. Based on the value, the caused-earthquake landslides potential is very small. This result does not rule out landslides caused by other factors, such as rainfall. Meanwhile, from the inversion method, it is found that the depth of the slip plane at the second location is about 11 to16 meters with a slope ranging from 23 to 33 .