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The Crustal Structure of Southwestern Turkey Using Local Seismic Data

Description: 

Oguzhan Yalvac, Eric Sandvol

In this study, we explore the crustal structure of southwestern Turkey (35°N-39°N and 26°E-32°E) using double difference travel time tomography. Travel time data were obtained from three different earthquake catalogs: International Seismological Centre (ISC), Kandilli Observatory and Earthquake Research Institute (KOERI), and The Disaster and Emergency Management Presidency of Turkey (AFAD). The ISC data was collected between the years 2000 and 2022, KOERI data from 2013 to 2021, and AFAD data from 2010 to 2022. Based on the location of intermediate depth seismicity in this region, the Hellenic slab is dipping to the west and the Cyprean slab is steeply dipping to the northeast. We have chosen 5437 very well-located earthquakes out of 191024 earthquakes. These events were relocated using the double difference approach (HYPODD). The Cyprean slab appears to become nearly vertical (or >80° dip angle) after relocation, while the Hellenic slab is still dipping to the west. The relocated earthquakes are concentrated on a line starting from the east of Kos Island and extending to the Fethiye-Burdur fault zone. This line of earthquakes might be evidence of an unnamed rift zone. In general, we observed evidence of the brittle-ductile at around 20 km depth, consistent with a fairly steep crustal geotherm.
The seismic velocity structure of the region was obtained by applying the double difference seismic tomography technique. Our preliminary tomographic model shows a low-velocity zone in the region extending from the east of Kos Island, which is the region with the most intense crustal seismic activity, to the Fethiye-Burdur Fault Zone. In addition, high Vp/Vs ratio and low Vp/Vs ratio anomalies were observed at the eastern edge of the Menderes Massif and in the northern part of the Menderes Massif, respectively. The accuracy of the results of the seismic tomography study has been evaluated using a large number of resolution tests. In addition to the resolution tests, we have utilized a bootstrap resampling scheme to estimate the velocity uncertainty.

Session: Crustal Imaging of High Seismic Hazard Regions [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Oguzhan Yalvac

Student Presenter: Yes

Invited Presentation: 

Authors