A Mw 6.1 earthquake on 25 February 2022, at around 8:39 a.m. local time, struck Pasaman Barat Regency, West Sumatra, Indonesia, and was felt in Singapore and Malaysia. The hypocenter of this earthquake was 12 km deep and preceded by an Mw 4.9 foreshock a few minutes earlier. The earthquakes originated on a blind fault and triggered a landslide at Mount Talamau. Herein, the slip distribution and asperities along the plane fault during the earthquake were examined by teleseismic inversion and the fault location was identified by Global Gravity Model plus (GGMPlus) satellite gravity data. The slip distribution was calculated from the source parameters (strike: 136°; dip: 70°; rake: 174°) by inversion techniques based on teleseismic data. Based on the slip distribution, the earthquake was generated by stress from the Sianok fault that spread to the north and reached the uncertain fault segment in the Talamau area. In addition, the results of the First Horizontal Derivative and Second Vertical Derivative from the GGMplus data revealed a straight Simple Bouguer Anomaly pattern, confirming the existence of the uncertain Talamau fault as part of the Great Sumatra Fault. This work shows the potential application of the combination of teleseismic and gravity observation for delineating the fault structure that caused the 2022 Mw 6.1 Pasaman earthquake, which can also be applied to other locations of similar geological backgrounds.

On December 14, 2021, an earthquake with a magnitude of 7.4 originated from the Flores Sea, impacting Kalaotoa Island in Indonesia, resulting in significant structural damage. Macroseismic observations at the site classified that there were 120 buildings slightly damaged, 108 buildings moderately damaged, and 201 buildings heavily damaged. The shakemap shows that Kalaotoa Island experienced VI-VII MMI shaking. The results of the field survey showed many indications of subsidence as many fractures were found in Kalaotoa Island. This study employed Differential Interferometry Synthetic Aperture Radar (DInSAR) to quantify land subsidence and uplift in Kalaotoa Island before and after the earthquake. Sentinel-1A satellite radar data from December 2 and December 14, 2021, were analyzed. The results revealed subsidence of up to 12 cm in Garaupa Raya Village and uplift of up to ±10 cm in Lembang Mate’ne Village. Approximately 50.50% of Kalaotoa Island experienced subsidence (39.4 km²), primarily in Garaupa Village (18.85 km²), while 49.02% of the island experienced uplift (38.2 km²), mostly in Lembang Mate’ne Village (19.03 km²). This spatial analysis underscores the efficacy of DInSAR in detecting and mapping surface deformation, offering critical insights for earthquake preparedness, mitigation efforts for impacted landscape topography, stability soils, structure of ecosystems, and infrastructure resilience.

Pada tanggal 15 Januari 2021, pukul 02.28 WITA 2021 terjadi gempa bumi signifikan dengan magnitudo M 6,2 di wilayah pesisir barat pulau Sulawes. Gempa bumi tesebut disebabkan oleh aktivitas sesar lokal Mamuju dengan pola patahan naik (Thrust Fault). Gempa bumi majene-Mamuju memberikan dampak kerusakan yang besar pada konstruksi bangunana yang berada dipermukaan khususnya pada wilayah kota Mamuju yang menjadi ibukota wilayah Sulawesi Barat. Perlu adanya evaluasi untuk menganalisis dan memodelkan ancaman dampak gempa bumi di wilayah kota Mamuju. Salah satu motode yang dapat digunakan untuk mengevaluasi kerentanan seismik suatu wilayah dapat menggunakan metode Horizontal to Vertical Spectral Ratio (HVSR). Data yang digunakan merupakan data sinyal microtremor dari hasil pengukuran lapangan sebanyak 39 titik menggunakan portable seismometer TDS-303 jenis short period. Terdapat empat parameter output yang dapat digunakan untuk menganalisis dan engevaluasi kerentanan seismik yaitu frekuensi dominan (f0), faktor amplifikasi (A0), indeks kerentanan seismik (Kg), dan periode dominan (T0). Dari hasil pengukuran di lapangan, maka output HVSR tersebut dapat dipetakan untuk mengiterpretasikan sebaran data secara spasial. Hasil penelitian menunjukkan jika wilayah kota Mamuju memiliki nilai frekuensi dominan (f0) antara 0,608 Hz-0,97 Hz, faktor amplifikasi (A0) antara 1,01-7,69, indeks kerentanan seismik (Kg) antara 0,468-73,886, dan periode dominan (T0) antara 0,09 s-1,64 s. Dari hasil tersebut wilayah kota Mamuju yang berada dekat dengan pesisir pantai memiliki potensi kerentanan terhadap bahaya gempa bumi yang jauh lebih tinggi, jika dibandingkan dengan wilayah yang berada di sebelah selatan. Hal ini juga didukung oleh hasil perhitungan ketebalan sedimen yang berkisar antara 7,6 m-130,2 m dengan wilayah utara jauh lebih tebal dari wilayah sebelah selatan. Sehingga wiilayah pesisir kota Mamuju relatif lebih rentan terhadap potensi amplifikasi gelombang seismik dipermukaan.

The Purpri Fault, a newly identified active fault in East Kolaka, Indonesia, has been analyzed using an integrated geophysical approach, combining HypoDD earthquake relocation and DInSAR ground deformation analysis. The relocation of 233 seismic events from January 24 to February 7, 2025, revealed a fault structure distinct from the Middle Kolaka and North Kolaka Faults, characterized by an oblique?normal faulting mechanism with a left?lateral component. The focal mechanism solution confirms significant vertical displacement, indicating a fault that accommodates both extensional and shear deformation. DInSAR analysis using Sentinel?1A SAR imagery detected subsidence and uplift patterns that align with the relocated seismicity, confirming ongoing crustal deformation along the Purpri Fault. The western block of the fault exhibits a subsidence of approximately ?13 cm, while the eastern block shows uplift of +11 cm, consistent with the seismic activity. The integration of seismic relocation and deformation mapping interpretation confirms that the Purpri Fault is an independent and active fault system. The shallow depth of seismicity (<10 km) and evidence of ongoing deformation indicate a potential seismic hazard that is not currently accounted for in regional seismic hazard models. Given its capacity to generate moderate to strong earthquakes, incorporating the Purpri Fault into updated seismic risk assessments is essential for improving earthquake preparedness and hazard mitigation strategies in East Kolaka.

The Maros-Pangkep region in South Sulawesi is a tropical karst landscape not officially mapped as an active fault zone, yet it has exhibited increasing micro-seismic activity in recent years. This study investigates the potential existence of hidden faults through hypocenter relocation using the double-difference method. A total of 191 earthquake events with magnitudes of 1-2.6 were successfully relocated using BMKG catalog data and the IASP91 global velocity model. The resulting hypocenters form a northwest–southeast-trending cluster, with fault plane geometry of 333°–346° strike, 8°–9° dip, and ~11 km length. These events cluster along boundaries of the Tonasa, Camba, and intrusive rocks, where competence contrast and karstification localize deformation. To complement the spatial analysis, magnitude–frequency characteristics were evaluated using the Gutenberg–Richter relationship. The estimated b-value of 1.34 indicates a low-stress regime dominated by small-magnitude seismicity, consistent with distributed deformation in brittle, heterogeneous lithologies. Although micro-seismic in scale, the spatial and statistical patterns suggest the presence of a structurally weak and potentially seismogenic zone that is not reflected in current tectonic maps. These findings underscore the importance of including the Maros–Pangkep region of South Sulawesi in seismic hazard assessments and land management efforts. The integration of relocation techniques and seismicity statistics proves effective for detecting latent fault structures in complex karst settings. In addition to seismic risks, such activity may accelerate land degradation through sinkholes, aquifer disruption, and ground instability, highlighting the value of geophysical assessments in managing vulnerable karst environments.