The 2001 M7.6 Earthquake Southwest of Punta de Bombón, Peru

The coastal region of southern Peru near Punta de Bombón lies within one of the world's most seismically active zones. This area forms part of the Peru-Chile Trench, where the Nazca Plate subducts beneath the South American Plate at a rate of approximately 6–7 cm per year. The resulting compressional forces generate frequent megathrust earthquakes, volcanic activity in the Andean cordillera, and ongoing crustal deformation. On 7 July 2001 at 09:38 local time, a magnitude 7.6 earthquake struck 51 km southwest of Punta de Bombón at a depth of 33 km. The event occurred in the immediate vicinity of the plate interface, consistent with typical subduction-zone seismicity. Because the hypocenter was relatively shallow, strong ground shaking was felt along the southern Peruvian coast, particularly in the Arequipa and Moquegua regions. The earthquake belongs to the sequence of large events that have repeatedly affected this segment of the margin. Southern Peru has a well-documented history of great earthquakes. Major ruptures occurred in 1604, 1784, 1868, and 2001, with the 1868 event producing a destructive tsunami that reached heights exceeding 10 m. These historical earthquakes demonstrate that the plate boundary in this area is capable of releasing accumulated strain in events of magnitude 8 or greater. The 2001 M7.6 earthquake is therefore interpreted as either a large aftershock or a triggered event within the broader seismic cycle of the southern Peru subduction segment. Geological studies of the region indicate that the subducting Nazca Plate exhibits variable coupling along strike. The segment offshore Punta de Bombón shows moderate to high coupling, allowing stress to build over decades to centuries before release. Post-seismic deformation following the 2001 event continues to be monitored by GPS networks, revealing afterslip and viscoelastic relaxation that redistribute stress both along the trench and inland. The local geology consists of a narrow coastal plain underlain by Quaternary marine terraces and alluvial fans, bordered by the steep western slope of the Andes. These terraces record long-term uplift driven by repeated subduction earthquakes. Offshore, the trench axis lies at depths greater than 6,000 m, with thick sedimentary fill that can influence rupture propagation. Since 2000, the region has experienced only this single M7.6 event meeting the threshold for strong earthquakes. Ongoing seismic monitoring by the Instituto Geofísico del Perú and international networks continues to track background seismicity and possible precursory signals. Updated hazard assessments incorporate both historical rupture data and modern geodetic measurements to refine estimates of recurrence intervals for future large events.

References

USGS Earthquake Catalog (event details for 7 July 2001). Instituto Geofísico del Perú seismic bulletins. Plate Boundary Observatory and regional GPS studies on Nazca–South America convergence.