Determination the Magnitude of Completeness, b-Value and a-Value for Seismicity Analysis in East Java, Indonesia

Abstract

Abstract Determine of magnitude of completeness (Mc), b-value and a-value are essential for a correct interpretation of seismicity analysis earthquake catalogue IRIS of East Java, Indonesia during the period 1990-2020. All estimated parameters were analyzed by apply The Maximum Curvature (MAXC) method. This method is a fast and straightforward way to estimating Mc and consists in determining the point of the maximum curvature by calculating the maximum value of the first derivative of the Frequency-Magnitude distribution (FMD) curve. In practice, this matches the magnitude bin with the highest occurrence frequency of events in the cumulative and non-cumulative of FMD. The value of the magnitude of completeness, which was evaluated on the frequency-magnitude distribution, was found range from Mc 3.4 to 4.0. Then, b-value (0.73 to 0.82 ± 0.02) and a-value 5.560 to 6.312 was obtained for the area Wongsorejo and the Montong faults in East Java and which is characterized by more heterogeneous crustal structure. The areas that have low b-value indicated as the area with a high seismic moment release and high stress accumulation. Low b-value areas are located mainly along the Java Trench. Seismicity of East Java is a result of the combined impacts of complex tectonic features. Understanding and clarifying the mechanisms of these tectonic features in relation to Mc, b-value and a-value can help us to better assess seismic risk in subduction zones.