Analisis Variasi b-value dan a-value Menggunakan Perangkat Lunak ZMAP Sebagai Indikator Potensi Gempabumi di Wilayah Jawa Timur: Analysis of b-value and a-value Variations Using ZMap Software as an Indicator of Earthquake Potential in the East Java Region

Saefurohmah, Mufti
Susanti, Dwi Budi
Sugito, Sugito
Maulita, Ika

Jurnal Stasiun Geofisika Sleman (JSGS)
Vol. 3 No. 2 (2025): Jurnal Stasiun Geofisika Sleman (JSGS) - Desember 2025

East Java is one of Indonesia's regions with a high level of seismicity due to its proximity to the subduction zone and the presence of active local faults. This study aims to analyze seismotectonic parameters, including a-value and b-value, as indicators of seismicity level and earthquake magnitude–frequency distribution characteristics. The analysis was conducted using the Maximum Likelihood method implemented in ZMAP. The earthquake data were obtained from BMKG and IRIS, covering the period from January 2004 to August 2024. The results indicate that East Java exhibits a high level of seismicity, with a value of 6.17 and a b-value of 0.757. Areas with relatively high earthquake activity potential were identified in Blitar, Tulungagung, and Trenggalek Regencies. The average seismicity index of East Java is 6.002, with a relatively short earthquake recurrence interval. These findings indicate a high potential for earthquake occurrence in East Java and may serve as a preliminary basis for sustainable earthquake disaster mitigation planning.