Location:

Period:

28 Oct 2022 14:21:28 - 29 Oct 2022 20:45:35 (1 day 6 hours 24 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

4 swarms found nearby.

2007

PS20070628.1(194.2km)

28 Jun

17 hours

6 earthquakes

PS20070816.1(92.7km)

15 Aug

3 days 20 hours

28 earthquakes

PS20070816.2(31.0km)

16 Aug

8 hours

6 earthquakes

2011

PS20111028.1(27.4km)

28 Oct

4 hours

5 earthquakes

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Seismic Swarm PS20221029.1: Analysis of Recent Activity Near Santiago, Peru

A notable seismic swarm designated PS20221029.1 occurred approximately 66 km west-southwest of Santiago, Peru, between 14:21 on 28 October 2022 and 20:45 on 29 October 2022. Over this 30-hour period, six earthquakes were recorded, with magnitudes ranging from 5.1 to 5.9 and focal depths between 8 and 26 km. This event highlights the persistent tectonic stresses in the region.

The sequence began with a magnitude 5.2 event at 14:21 on 28 October at 20 km depth. Subsequent shocks included a magnitude 5.9 at 20:22 (14 km depth), followed by three magnitude 5.2 events at 22:52 (8 km), 23:35 (10 km), and a magnitude 5.8 at 00:09 on 29 October (15 km depth). The swarm concluded with a magnitude 5.1 event at 20:45 on 29 October at 26 km depth. These closely spaced events reflect typical swarm behavior, characterized by multiple moderate tremors without a single dominant mainshock.

Peru lies along the active subduction zone where the Nazca Plate converges with the South American Plate at rates of approximately 6–7 cm per year. This tectonic setting drives frequent seismicity along the Peru-Chile Trench, with the coastal and near-coastal areas experiencing both interface and intraslab earthquakes. The Santiago region, situated in northern Peru, sits within this convergent margin, where historical records document repeated moderate-to-large events linked to plate boundary dynamics.

Seismic swarms in this area are not uncommon. Since 2000, four such swarms have been documented, with earlier episodes occurring in 2007 (three events) and 2011 (one event). These clusters often arise from fluid migration or stress transfer along faults, providing insights into the evolving stress field without necessarily signaling an imminent larger rupture.

Geological studies of the Peruvian margin emphasize the role of the subducting Nazca Ridge and variations in slab geometry in modulating seismicity patterns. Depths recorded in the recent swarm align with both shallow crustal and upper-plate activity, consistent with the complex fault networks onshore and near the trench. Ongoing monitoring by regional networks continues to refine understanding of these processes.

SeismoSight internal swarm classification PS20221029.1
Regional tectonic framework from plate convergence models (USGS Earthquake Hazards Program)