Analysis of a-Value and b-value parameters for earthquake disaster mitigation around the Saddang Fault

Abstract Sulawesi Island is one of the areas with a fairly high level of seismicity and the potential for tectonic earthquakes. In 2018 there was an earthquake in Palu, Mamasa, and Mamuju which resulted in many casualties and property. The earthquake that occurred in Mamasa was the impact of the activity of the Saddang Fault. The study was conducted to find out how seismic activity and the level of brittleness of rocks in the area are. The location of the study is at the coordinates 2.50 S – 3.46 S and 118.6 E – 120.3 E. using earthquake data from the USGS from 1970 to 2023 and processed using Zmap 7 software. The results of the study obtained a value of a = 5.683 which means that the earthquake activity around the Saddang Fault is relatively low. This is reinforced by an annual value of 3.973 or equal to 4, which is a value that shows the number of earthquake events each year. B-value = 0.87 ± 0.13 or ranges from 0.74 – 1.0 and is in the medium category. This value indicates the level of brittleness of the rock. Areas with low rock fragility have low seismic activity but higher magnitude than in areas with higher rock fragility. Rocks with a low level of fragility are able to store a large enough amount of energy so that in the event of an earthquake it will produce a large amplitude, and vice versa. In this study, the Mc value = 4.6, which is the lower limit of the earthquake magnitude value. From the above results, it is important to continue to monitor seismic activity in this region and develop strategies for disaster mitigation so that casualties can be minimized.