Observations of Repeating Earthquakes at a Single Seismic Station Near Lake Sapanca

Year 2023, Volume: 23 Issue: 6, 1533 - 1541, 28.12.2023

Diğdem Acarel

https://doi.org/10.35414/akufemubid.1286692

Abstract

The North Anatolian Fault Zone (NAFZ), which forms the plate boundary between Anatolian Plate and Eurasian Plate, is one of the most active transform fault zones in the world. Following two consecutive magnitude M>7 earthquakes in 1999, an intensified monitoring of western portion of NAF is commenced. Dense networks of onshore/offshore seismic, acoustic, geodetic sensors and surface creep and strain sensors were installed. A single seismic sensor among these, which is located at the midpoint of 1999 ruptures, near Lake Sapanca, exhibits some unusual seismic activity. On a fault segment where creep is known to be present, a series of minor seismic events was observed with identical locations and a recurrence time of three years. These events are quite short in duration and highly similar in their waveforms. Using a single station approach, their angle of incidence and back azimuth were found to coincide with the location of two M2.3 and M2.1 events. At this stage, it is not clear whether these events reflect fault creep at seismogenic depth. Nevertheless, these initial observations emphasize the necessity of monitoring this segment more densely, where recurrent minor earthquakes are likely to be observed.

Keywords

Creep, Lake Sapanca, North Anatolian Fault, Repeating Earthquakes, Single Seismic Station

Project Number

117C009

Sapanca Gölü Yakınında Tek Bir Sismik İstasyonda Tekrarlayan Deprem Gözlemleri

Abstract

Kuzey Anadolu Fay Zonu (KAFZ), Anadolu ve Avrasya plakaları arasındaki levha sınırını oluşturur ve dünya üzerindeki en aktif transform faylarından biridir. 1999'da meydana gelen iki M>7 depremin ardından, KAF'ın batı kısmı yoğun bir şekilde izlenmeye başlanmıştır. Karada/denizde yoğun ağlarla sismik, akustik, jeodezik, yüzey kripi ve gerinimi ölçen sensörler kurulmuştur. Bu sensörler arasında, 1999 kırılmalarının merkezinde, Sapanca Gölü yakınlarında bulunan tek bir sismik sensör, bazı olağandışı sismik aktiviteler kaydetmiştir. Krip gözlemlenen bir fay segmentinde, aynı konumlarda, üç yıllık tekrarlama süresi ile küçük sismik olaylar gözlemlenmiştir. Bu olaylar oldukça kısa sürelidir ve dalga formları açısından oldukça benzerdir. Tek istasyon yaklaşımı kullanılarak, bu olayların çıkış açısı ve geri azimut açısının M2.3 ve M2.1 büyüklüğündeki depremlerin konumuna denk geldiği bulunmuştur. Bu aşamada, bu olayların sismojenik derinlikte krip yansıtıp yansıtmadığı belirsizdir. Bununla birlikte, bu ilk gözlemler, tekrarlayan depremler gözlenen bu segmentin daha yoğun bir şekilde izlenmesinin gerekliliğini vurgulamaktadır.

Keywords

Kuzey Anadolu Fayi, Krip, Sapanca Gölü, Tekrarlayan Depremler, Tek Bir Sismik Istasyon

Supporting Institution

TÜBITAK

Project Number

117C009

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