Slip distribution and stress changes associated with the 1999 November 12, Düzce (Turkey) earthquake

Abstract

SUMMARY The 1999 November 12 Düzce earthquake (Mw= 7.1) was apparently the eastward extension of the August 17, İzmit earthquake (Mw= 7.4). The Düzce event caused heavy damage and fatalities in the cities of Düzce and Bolu. Here a finite‐fault inversion method with five discrete time windows is applied to derive the co‐seismic slip distribution of the Düzce earthquake. The fault plane is best modelled as a 40 × 20 km2 plane, with a strike of 262° and a dip of 65° to the north, and that the majority of slip occurred in two distinct patches on either side of the hypocentre, implying bilateral rupture. The possible triggering of this event by the İzmit earthquake is investigated using Coulomb stress modelling of all large events since 1943 with the inclusion of secular loading. The results show that although the Düzce rupture plane was in a stress shadow prior to the İzmit earthquake, that event caused a significant Coulomb stress load, taking the Düzce fault out of the stress shadow, which probably precipitated failure. A comparison of the mapped Coulomb stress change with the inferred slip shows no correlation between the two. Finally, the stress modelling indicates that the northern branch of the North Anatolian fault zone, beneath the Sea of Marmara towards the city of İstanbul, is presently the most highly loaded segment of the North Anatolian Fault Zone.

Spatial variation of the stress field along the fault rupture zone of the 1999 Izmit earthquake

“…For example, the 1992 Landers earthquake (M w 7.3) ruptured ve distinct fault segments with different geometries separated by releasing and restraining step-overs (Sieh et al, 1993). This multi-segment rupture pattern is a characteristic feature of the large NAFZ earthquakes generating complex waveforms and has been observed in the 1992 Erzincan (M w 6.8) and 1967 Mudurnu Valley (M w 7.1) earthquakes (P nar et al, 1994, 1996Barka, 1996) and, most recently, in the 1999 Izmit and Düzce earthquakes (Gülen et al, 2002;Utkucu et al, 2003).…”

Temporal Changes of Shallow Seismic Velocity Around the Karadere-Düzce Branch of the North Anatolian Fault and Strong Ground Motion

“…Three months later, this segment reruptured during the Du¨zce main shock (e.g., HARTLEB et al, 2002). The 28 clusters in the Eften Lake area are in the depth range of 5-10 km, and appear to be on a fault plane dipping $65 o north (UTKUCU et al, 2003). The other 12 clusters are located along the Karadere segment that ruptured during the _ Izmit main shock.…”

Seismic behaviour of the North Anatolian Fault beneath the Sea of Marmara (NW Turkey): implications for earthquake recurrence times and future seismic hazard

“…These studies have comprised reassessment of historical seismicity (Ambraseys and Jackson 2000;Ambraseys 2001aAmbraseys , b, 2002a, monitoring of microseismicity (Sato et al 2004), high-resolution bathymetry and multi-channel seismic reflection studies (Okay et al 2000;Le Pichon et al 2001;Armijo et al 2002Armijo et al , 2005Parke et al 2002;Gökaşan et al 2003;Demirbag et al 2003;McHugh et al 2006;Kanbur et al 2007), earthquake focal mechanism-derived stress orientations (Polat et al 2002;Pınar et al 2003), field geology (Altınok et al 2003;Seeber et al 2004;Okay et al 2004;Altunel et al 2004), paleoseismology (Rockwell et al 2001;Klinger et al 2003;McHugh et al 2006), Coulomb static stress change modelling (Hubert-Ferrari et al 2000;Parsons et al 2000;Utkucu et al 2003;Parsons 2004;Lorenzo-Martin et al 2006;Pondard et al 2007), space geodesy (Meade et al 2002;Flerit et al 2003) and earthquake probability (Parsons et al 2000;Parsons 2004;Cisternas et al 2004) studies. The basin of the Sea of Marmara was considered as a rift with a strike parallel to the proposed western Turkey rift system in the earlier phase of the construction of the plate kinematics of the eastern Mediterranean region (McKenzie 1972).…”