Fault Lines Affecting Batangas, including Newly Discovered Ones
This article synthesizes peer-reviewed studies, institutional reports, and high-resolution geophysical surveys to present a comprehensive account of the fault systems in and around Batangas Province that are implicated in its earthquake activity. Every factual claim below is grounded on published geophysical data, PHIVOLCS bulletins, or institutional syntheses; citations are given in order of appearance.
Batangas lies within a structurally complex portion of the Philippine Mobile Belt, a region of the Earth’s crust that has been tectonically active for long geological periods. Several sets of interacting faults — some long known on land, others only recently mapped offshore — accommodate crustal strain between the Manila Trench and the Philippine Fault Zone.
Modern bathymetry (the study and measurement of the depths and shapes of underwater terrain), seismic-reflection profiles, and earthquake relocations reveal that southwestern Luzon contains an interconnected conjugate or connected network of NW-trending right-lateral faults and E–W left-lateral faults. This geometry explains why moderate to large earthquakes may originate offshore yet produce strong shaking onshore in Batangas.1
The Batangas Bay Fault System (BBFS) is a NW-trending right-lateral fault system beneath Batangas Bay, identified through high-resolution marine seismic surveys. It was implicated in the 2017 Batangas earthquake sequence and is capable of producing shallow, damaging quakes that affect Batangas City, Bauan, and Mabini.2
Offshore strands between the Calumpang (Mabini) Peninsula and Maricaban/Tingloy islands — sometimes referred to as the Maricaban Fault — were also resolved in marine surveys. These structures explain the clustering of hypocenters — a hypocenter being the exact point inside the Earth where an earthquake originates — during the 2017 earthquake swarm in the Mabini–Tingloy sector.3
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| Active fault map for Batangas from the PHIVOLCS web site. For full resolution version, visit Phivolcs. |
The Balayan Fault and the Calatagan Fault form onshore or near-coast members of the NW right-lateral family. Regional mapping lists these as principal faults that bound or run near Balayan Bay and the Calatagan peninsula.4
The Aglubang River Fault in Oriental Mindoro ruptured on November 15, 1994, during a magnitude 7.1 earthquake. The event produced clear surface ruptures along the Aglubang River and generated a destructive tsunami. Stress modeling later showed that this rupture transferred strain onto faults affecting Batangas, including the Batangas Bay system.5
South of Batangas runs the Verde Passage Fault System, composed of the North, Central, and South Verde Faults. These are E–W trending left-lateral structures mechanically linked with the Lubang Fault to the northwest. They interact with the NW-trending Batangas Bay and Balayan faults, forming the conjugate pattern characteristic of this tectonic setting.6
The Central Mindoro Fault (CMF) is another active left-lateral fault in Mindoro that forms part of this wider network. It has been studied for its role in accommodating strain west of Batangas and its interaction with both the Aglubang River and Verde Passage systems.7
More recently, onshore faults in Batangas such as the Lobo Fault System and the Calubcub Fault near San Juan have been identified through detailed field mapping. These structures were not part of older PHIVOLCS maps but are now recognized in updated regional inventories of active faults.8
PHIVOLCS has also documented earthquake swarms beneath Mabini and Tingloy, most notably in April 2017. These were initially described as the result of movement on a “local fault” in the area. Later geophysical studies confirmed their link to offshore strands of the Batangas Bay system.9
In summary, Batangas is not free of faults, contrary to older assumptions. It is bounded and underlain by a partly offshore, conjugate fault network that includes the Batangas Bay, Maricaban, Balayan, and Calatagan faults; the Verde Passage and Lubang systems; the Central Mindoro and Aglubang River faults; and onshore structures like the Lobo and Calubcub faults. Earthquakes in recent decades, especially 1994 and 2017, show that these structures are active, hazardous, and central to understanding Batangas’s seismic history.10
2 “Sarmiento Seafloor Structures 2022,” UP Marine Science Institute, 2022, online at msi.upd.edu.ph.
3 “Primer on the April 2017 Series of Earthquakes in Batangas Province,” PHIVOLCS, 2017, online at phivolcs.dost.gov.ph.
4 “Shaken Again? Unraveling the Sources of Earthquakes in Southwestern Luzon, Philippines,” PreventionWeb (UNDRR/PHIVOLCS), 2020 online at www.preventionweb.net.
5 “Field Report on the November 15, 1994 Mindoro Earthquake,” Earthquake Engineering Research Institute, 1995, online at www.eeri.org.
6 “Active Faults in the Verde Island Passage and Southwestern Luzon,” PHIVOLCS Technical Report, 2019, online at phivolcs.dost.gov.ph.
7 “The Central Mindoro Fault: An Active Sinistral Fault in Southwestern Luzon,” Rimando, R. et al., 2025, MDPI Earth journal, online at www.mdpi.com.
8 “Regional Active Fault Mapping of Southwestern Luzon,” Llamas, D.C.E. et al., 2022, online at researchgate.net.
9 “Earthquake Information: Batangas Earthquake Swarm 2017,” PHIVOLCS, 2017, online at phivolcs.dost.gov.ph.
10 “Coulomb Stress Modeling of Earthquakes in Batangas and Mindoro,” Sarmiento, K.J.S. et al., 2022, Frontiers in Earth Science, online at www.frontiersin.org.