Seismic Hazard Measurement of Earthquake Swarms Activity Based on Horizontal Vertical to Spectral Ratio Analysis (HVSR) in West Halmahera, Indonesia

Abstract

The swarm earthquake that occurred in West Halmahera which recorded a lot resulted in damage to houses in several rural areas. Although human casualties are not too significant, they affect the stability and capacity of an area in terms of regional development. Mapping of seismic hazard zone is a solution to minimize the impact that will be caused by the earthquake. The purpose of the study is to initial mapping seismic hazard zoning based on Horizontal Vertical to Spectral Ratio (HVSR) analysis. The estimated values of the fundamental frequency range from 0.0 Hz up to 4.9 Hz increases with decreasing depths of basement rock. Regions with the lowest dominant frequency value are South Ibu sub-District, this shows that the area has a large sediment thickness and is a vulnerable area of high. Amplification value range of 4.7 – 51, where the higher the amplification value, the thickness of sediments. The highest amplification value area is Jailolo sub-District and is an area that has a high risk of damage if shaken by an earthquake. This shows that areas that have high amplification values are areas that have the greatest potential for damage due to earthquakes. Analysis obtained from the results of the data shows that the topographic influence is also very significant with the earthquake waves that occur.

Characterization of the Mamasa Earthquake Source Based on Hypocenter Relocation and Gravity Derivative Data Analysis

“…The dominance of granite and the thin layer of sediment make the city an area with a low damage potential during an earthquake. The thicker the sediment is, the higher the amplification value and the higher the risk of damage from an earthquake [34]. In addition, the dominance of granite and thin sediment layers makes the depth of the basement very shallow.…”