GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 position after tomography at each step of the iterative procedure, based on the conversion of time residuals to depth using the local velocity model. With some synthetic examples we will try to verify the reliability of the proposed method. The method This method uses an iterative procedure “Location + Travel Time Tomography”, where, after each tomographic step, the earthquakes depths are upgraded by using time residuals. The depth correction is performed by converting the average of the time residuals of all stations of each earthquake into depth: = − 1 =1 ∑ ( ) where NS is the number of stations associated to each single event, is the vertical ( ) component of , is the time residual associated to the i-th station, and is the model velocity crossed by the ray path starting from the source (earthquake) and reaching the i-th station (see the scheme in Fig. 1). Fig.1 – a) Depth correction applied to the Z coordinate of each event from the residual analysis in case of dt < 0 (ray A) and dt > 0 (ray B). b) Scheme of the procedure describing the method presented in this work. The adopted procedure consists of the following steps, the schematic sequence of which is shown in Fig. 1: