Determination of upper-crust velocity structure (1-D) of the Erzincan basin and its surroundings

Bu çalışmada, Erzincan havzası ve dolayına ait 1-B P- ve S- dalgası hız yapısının bulunması amaçlanmıştır. 13 Mart 1992 Erzincan depremine (Mw=6.9) ait 1548 artsarsıntının 22250 P- ve 10184 S- varış zamanı, çözümlemeler için kullanılmıştır. Tüm veri grubu içerisinden GAP <180?  ve en az 10 P- ve 5 S- fazına sahip artsarsıntılar seçilmiş olup 1-B hız yapısının hesaplanmasında VELEST isimli yazılım kullanılmıştır. Artsarsıntılar, 0-22 km derinlikte meydana geldiği için, bu aralıktaki katmanlar, ters çözüm sonucu daha iyi belirlenebilmiştir. Sonuç olarak; elde edilen 1-B hız modeli ile bölgenin altı farklı hız katmanına sahip olduğu bulunmuştur.Anahtar Kelimeler: 13 Mart 1992 Erzincan depremi, 1-B hız yapısı, 1-B ters çözüm, yerel deprem çözümlemesi.In this study, we aimed to obtain upper-crust 1-D P- and S- wave velocity structure of  the Erzincan basin and its surroundings and to find accurate hypocentral parameters. 22250 P- and 10184 S- arrival times that belong to 1548 aftershocks of the March 13, 1992 Erzincan earthquake (Mw=6.9) were used for  calculations. The stations that have Telemetry, Geostras, MEQ, Reftek and MLR type recorders were consist of  sismometers with both vertical and tree-components. VELEST was used to calculate minimum 1-D velocity structure of the region for both P- and  S- wave. A subset of all data set was prepared by selecting well locatable afterhocks have GAP <180?, least 10 P- and 5 S- phase readings. 979 aftershocks which have 17121 P- phases for P- velocity model and 926 afterhocks which have 16877 P- and 8384 S- phases for P&S velocity model were used for iterative simultaneous inversion computing. Since almost all earthquakes occurred a depth range  0-22 km  in the upper-crust, thickness and velocity of the layers were determined more accurately in this depth range. As a result, it was found that the region has six different velocity layers at the end of the 1-D inversion. The calculated 1-D velocity model will be a initial model for 3-D tomography and also it will be able to used as a reference model for seismologic studies.  Keywords: 13 March 1992 Erzincan earthquake, 1-D velocity structure, 1-D inversion, local earthquake analysis