The earthquake occurred on Friday, January 14, 2022, at 16:05:41 WIB in the Pandeglang Regency, Banten. According to the Meteorology, Climatology and Geophysics Agency (BMKG), the epicenter of the earthquake was precisely located at 105.05 East Longitude and 7.01 South Latitude in the southwest direction with an earthquake magnitude of 6.7 Mw and at a depth of 10 km. The location is under the sea but has no potential for a tsunami.

Earthquake shocks were felt quite strongly, especially around the location of the epicenter, with an estimated intensity of around VI-VII Modified Mercalli Intensity (MMI) (Figure 1). In Jakarta and surrounding areas, the intensity ranges from III-IV MMI, while in Bandung and surrounding areas II-III MMI. The earthquake caused damage to buildings in the Lebak and Pandeglang regencies, Banten province. Until now, the Center for Volcanology and Geological Hazard Mitigation (PVMBG) is still monitoring for more information.

Figure 1. Earthquake intensity map on Friday January 14, 2022 (BMKG, 2021)

Based on earthquake data and analysis information from other sources such as GeoForschungsZentrum (GFZ), there are slight differences in the magnitude, location, and depth of the earthquake (Table 1), where the strength of the earthquake was 6.5 Mw at locations 105.37 East Longitude and 6.80 East Longitude. LS at a depth of 38 km.

Table 1. Earthquake data with focal mechanism solution from GFZ

This depth difference is the subject of further study reviews because the location of the earthquake point is close to subduction tectonic provinces and also shallower fault structures such as the Cimandiri fault, as well as horizontal faults and down faults in the Sunda Strait. The focal mechanism data identified by GFZ show the existence of an ascending fault kinematics with a northwest-southeast trending fault marked by the P-axis trending southwest-northeast and the T-axis approaching vertical. This pattern follows the pattern of the subduction zone in the south of Java, namely the subduction zone of the Indo-Australian plate under the Eurasian plate (Figure 2).

Figure 2. Distribution of earthquake data around Indonesia (USGS, 1960-2018). Dark blue 0-60 km, light blue – green 60-150 km, yellow-orange 150-250 km, pink 250-300 km and white 300-700 km.

Figure 3 shows the structural pattern in the Java Island and its surroundings. The structural pattern formed by tectonic subduction in the southern part of the island of Java tends to be co-axial. The impact of these geological processes formed a mega-thrust in the south of Java, a rising fault in the prism of accretionary zone, as well as a rising fault and folds on the mainland of the island of Java. However, if you look closely, the structure that develops in the Java area is not only focused on rising faults, the movement of horizontal faults also has quite intense activity. For example, the Cimandiri fault, the Opak fault, the Garut fault and other horizontal faults. The analysis of the focal mechanism solution (FMS) <70 km has shown that the fault kinematics that caused the earthquake in recent years are dominated by rising faults and horizontal faults. However, the fault activity that caused the earthquake that occurred on January 14, 2022 is closely related to other geological structures that caused the previous earthquake in the area near the epicenter (Figure 4).

Figure 3. Map of the structure of Java Island and its surroundings with BMKG and GCMT FMS (Focal Mechanism Solution) data overlays (earthquake depth <70 km) (Adhitama, 2020).

Figure 4. The location of the January 14, 2022 earthquake and the location of previous earthquakes accompanied by FMS data.

Reference:

https://geofon.gfz-potsdam.de/old/eqinfo/list.php?mode=mt 

https://news.detik.com/berita-jawa-barat/d-5898652/analisis-pvmbg-soal-penyebab-gempa-di-banten

https://www.bmkg.go.id/gempabumi/gempabumi-terkini.bmkg

https://www.globalcmt.org/CMTsearch.html