Abstract

On May 27th2006, Yogyakarta earthquake happened with 6.3 Mw. It was causing widespread destruction and loss of life and property. The average shear wave velocity to 30 m (Vs30) is useful parameter for classifying sites to predict their potential to amplify seismic shaking (Boore, 2004) [1]. Shear wave velocity is one of the most influential factors of the ground motion. The average shear wave velocity for the top 30 m of soil is referred to as Vs30. In this study, the Vs30 values were calculated by using multichannel analysis of surface waves (MASW) method. The Multichannel Analysis of Surface Waves (MASW) method was introduced by Park et al. (1999). Multi-channel Analysis of Surface Waves (MASW) is non-invasive method of estimating the shear-wave velocity profile. It utilizes the dispersive properties of Rayleigh waves for imaging the subsurface layers. MASW surveys can be divided into active and passive surveys. In active MASW method, surface waves can be easily generated by an impulsive source like a hammer, sledge hammer, weight drops, accelerated weight drops and explosive. Seismic measurements were carried out 44 locations in Yogyakarta province, in Indonesia. The dispersion data of the recorded Rayleigh waves were processed by using Seisimager software to obtain shear wave velocity profiles of the studied area. The average shear wave velocities of the soil obtained are ranging from 200 ms-1 to 988 ms-1, respectively.

Highlights

  • Yogyakarta is one of the high seismicity areas in Indonesia

  • The Nglanggran Formation mainly composed of coarsed volcanic materials such as andesitic breccias which grade upward into pebble conglomerates and andesitic sandstones

  • The multichannel analysis of surface waves (MASW) data was processed by using Seisimager software [13]

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Summary

Introduction

Yogyakarta is one of the high seismicity areas in Indonesia. Yogyakarta earthquake occurred with 6.3 Mw on 27th May 2006. The Yogyakarta province is high density of population. The shear wave velocity (Vs) of the sub-surface layer can be estimated using various seismic methods. Semilir Formation is mainly composed of interbedded breccias, shales and tuffs. The age of this formation is Late Oligocene to early Miocene. The Nglanggran Formation mainly composed of coarsed volcanic materials such as andesitic breccias which grade upward into pebble conglomerates and andesitic sandstones

General geology of Yogyakarta
Multi-channel analysis of surface wave method
Results and discussions
Conclusions

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