Application of 3-D Velocity Models and Ray Tracing in Double Difference Earthquake Location Algorithms: Application to the Mygdonia Basin (Northern Greece)

Abstract

In the past years there has been a growing demand for precise earthquake locations for seismotectonic and seismic hazard studies. Recently this has become possible because of the devel opment of sophisticated location algorithms, as well as hardware resources. This is expected to lead to a better insight of seismicity in the near future. A well-known technique, which has been re cently used for relocating earthquake data sets is the double difference algorithm. In its original im plementation it makes use of a one-dimensional ray tracing routine to calculate seismic wave travel times. We have modified the implementation of the algorithm by incorporating a three-dimensional velocity model and ray tracing in order to relocate a set of earthquakes in the area of the Mygdonia Basin (Northern Greece). This area is covered by a permanent regional network and occasionally by temporary local networks. The velocity structure is very well known, as the Mygdonia Basin has been used as an international test site for seismological studies since 1993, which makes it an ap propriate location for evaluating earthquake location algorithms, with the quality of the results de pending only on the quality of the data and the algorithm itself. The new earthquake locations re veal details of the area's seismotectonic structure, which are blurred, if not misleading, when resolved by standard (routine) location algorithms.

The Greek Database of Seismogenic Sources (GreDaSS): state-of-the-art for northern Greece

“…37 km. Field measurements along the fault trace [Pavlides and Tranos 1991] and the microseismicity distribution at depth [Galanis et al 2004] indicate a steeply dipping fault plane. On the basis of the available seismological information, the maximum depth of the structure is likely to be 16-18 km.…”

“…Field observations of slickenlines indicate a rake of 300˚-325˚ [Pavlides and Kilias 1987]. The three-dimensional relocation of a set of earthquakes to the Chalkidiki peninsula [Galanis et al 2004], indicate seismogenic depths down to 16-17 km for this zone, while a relocated seismic cluster suggests eastwards continuation of the fault zone offshore and north of Amoliani Island [Galanis et al 2004], thus defining a total length of ca. 30 km.…”

“…29 km), the maximum expected magnitude is 6.6 [Wells and Coppersmith 1994]. The westernmost section of the fault zone is characterized by microseismic activity [Galanis et al 2004, Paradisopoulou et al 2004]. According to three-dimensional re-location of the local seismicity [Galanis et al 2004], the thickness of the seismogenic layer is ca.…”

Comparison between single-event effects and cumulative effects for the purpose of seismic hazard assessment. A review from Greece

“…Microearthquake investigations (Hatzfeld et al, 1986/87;Tranos et al, 2003;Galanis et al, 2004;Paradisopoulou et al, 2006) constrain the seismogenic layer thickness down to a maximum depth of ca. 15 km (Fig.…”

Συμβολή Στον Προσδιορισμό Τρισδιάστατου Εδαφικού Προσομοιώματος Για Τη Μελέτη Της Σεισμικής Απόκρισης

“…Η βάση αυτή δεδομένων εμπλουτίστηκε από τις καταγραφές των προσωρινών σεισμομετρικών δικτύων που λειτούργησαν στην ευρύτερη περιοχή της Μυγδονίας. Οι κοινές καταγραφές των δύο δικτύων χρησιμοποιήθηκαν για τον επανακαθορισμό των επικέντρων (Galanis et al, 2004) και τον υπολογισμό των μηχανισμών γένεσης των σεισμών (Vamvakaris et al, 2004). Οι μεγαλύτεροι σεισμοί που καταγράφηκαν στο δίκτυο είναι ο σεισμός της Αρναίας 4/5/1995 (Μ w =5.8), της Κοζάνης 13/5/1995 (M w =6.6), της Λευκάδας…”