Enhancing Earthquake Detection During the 2023 Reykjanes Swarm Using the Extended IPF Method

In late 2023, the Reykjanes Peninsula in Iceland experienced an intense seismic and volcanic episode. A major earthquake swarm began on 24 October 2023, driven by magmatic intrusion beneath the region, and its frequency and intensity escalated dramatically on 10 November. This activity culminated in the Sundhnúksgígar crater chain eruption on 18 December. During the November swarm, the high density of tremors caused significant challenges for the automatic earthquake location system, reducing its reliability. To address this issue, we applied the extended Integrated Particle Filter (IPFx) method to continuous seismic data recorded during the eruption period.

The IPFx method, originally developed for Japan’s Earthquake Early Warning (EEW) system, integrates single-station P-wave detection with a network-based particle filter approach to estimate event locations and magnitudes in real time. It processes continuous waveform data from multiple stations, enabling rapid and accurate earthquake detection even during intense seismic sequences. We analyzed three days of continuous data (9–11 November 2023) and compared IPFx-derived locations with the manually reviewed catalog of the Icelandic Meteorological Office (IMO).

Initial application of the IPFx method using its default configuration—Japanese velocity structure and no historical seismicity—resulted in large offshore location uncertainties due to limited azimuthal coverage near the eruption site. To improve accuracy, we incorporated the South Iceland Lowland (SIL) velocity model used in Iceland and regional historical seismicity into the particle filter’s sampling and likelihood functions. These modifications reduced average location errors by approximately 50%. Furthermore, the IPFx method successfully distinguished multiple closely spaced events during periods of high seismicity, demonstrating its potential for generating reliable automatic earthquake catalogs under challenging conditions.

Our findings highlight the adaptability of the IPFx method for real-time seismic monitoring in volcanic regions with sparse station coverage. By improving earthquake location accuracy during swarm activity, this approach can enhance early warning capabilities and contribute to hazard mitigation efforts in Iceland and similar tectonic settings.