Seismic Swarm S20071107.1 Near the Coast of Western Turkey

Seismic swarm S20071107.1 occurred near the coast of western Turkey from 11:31 on 7 November 2007 to 17:04 on 9 November 2007. In 53 hours and 32 minutes, 47 earthquakes were recorded. The events clustered in a compact area consistent with the extensional tectonics of the Aegean region.

Magnitudes ranged from 2.3 to 4.0, with the largest event reaching 4.0 at a depth of 5 km on 7 November at 21:36:40. Multiple events of magnitude 3.8 occurred on 8 November at depths of 5 km. Depths were predominantly shallow, between 0 and 30 km, typical of crustal faulting in this zone. The sequence lacked a single dominant mainshock, characteristic of swarm behavior driven by fluid migration or localized stress redistribution along normal faults.

Western Turkey lies within the Western Anatolian Extensional Province, part of the broader Aegean tectonic regime. This area experiences north-south extension due to rollback of the Hellenic subduction zone and westward extrusion of the Anatolian plate. The North Anatolian Fault influences regional strain, while numerous active normal faults accommodate extension. Historical records document recurrent moderate seismicity along the Aegean coast, with notable events in the 20th century linked to these structures.

Since 2000, only two swarms have been identified in the region, with the first occurring in 2005. Such episodic clustering highlights the role of transient processes in modulating seismic release without producing large mainshocks.

The 2007 swarm provides insight into swarm dynamics in extensional settings. The tight temporal grouping and shallow focal depths suggest involvement of pressurized fluids or aseismic slip transients. Comparable patterns appear in other Aegean sequences, underscoring the value of dense monitoring for distinguishing swarms from foreshock-mainshock sequences.

References

• USGS Earthquake Catalog (historical data for western Turkey)
• Boğaziçi University Kandilli Observatory seismicity reports
• Journal of Geophysical Research: Solid Earth articles on Aegean extension (2000–2023 updates)