S U M M A R YWe investigate aftershock focal mechanisms of the M w = 7.4 Izmit earthquake of 1999 August 17, on the western North Anatolian fault zone (NAFZ). Spatial clustering and the orientation of 446 fault plane solutions are analysed. The Izmit mainshock occurred as a right-lateral slip on an EW-trending near-vertical fault plane. Aftershock clusters define four individual fault segments. Focal mechanisms surrounding the epicentres of the Izmit and subsequent Düzce mainshock (M w = 7.1, 1999 November 12) indicate predominantly strike-slip but also normal faulting. Aftershocks in the area between the Izmit and Düzce segments are mainly related to EW-oriented normal faulting delineating a small pull-apart structure. Beneath the easternmost Sea of Marmara, alignments of aftershocks suggest branching of the NAFZ into three or more active segments that differ significantly in terms of their focal mechanism characteristics. The distribution of aftershock focal mechanisms corresponds to fault segmentation of the NAFZ in the Izmit-Düzce region produced by coseismic slip. Areas with large amounts of coseismic slip show aftershocks that are predominantly strike-slip, but low-slip barriers show mostly normal faulting aftershocks.Stress tensor inversions of the aftershock focal mechanisms show rotations of the local stresses following the Izmit mainshock. In the Izmit-Sapanca area, the maximum horizontal compressive stress axis is horizontally rotated counter-clockwise by 8 • with respect to the coseismic and long-term regional stress field. Towards the eastern end of the rupture (KaradereDüzce area), stresses are rotated clockwise. We conclude that the Izmit earthquake caused significant stress partitioning along the rupture. The direction of stress rotation is related to the orientation of the individual fault segments along the NAFZ.

Mt. Merapi is one of the most dangerous volcanoes in Indonesia, located within the tectonically active region of south‐central Java. This study investigates how Mt. Merapi affected ‐ and was affected by ‐ nearby tectonic earthquakes. In 2001, a Mw6.3 earthquake occurred in conjunction with an increase in fumarole temperature at Mt. Merapi. In 2006, another Mw6.3 earthquake took place, concomitant with an increase of magma extrusion and pyroclastic flows. Here, we develop theoretical models to study the amount of stress transfer between the earthquakes and the volcano, showing that dynamic, rather than static, stress changes are likely responsible for the temporal and spatial proximity of these events. Our examination of the 2001 and 2006 events implies that volcanic activity at Mt. Merapi is influenced by stress changes related to remote tectonic earthquakes, a finding that is important for volcano hazard assessment in this densely inhabited area.

SUMMARY We derive the rupture history of the 1999 August 17 Izmit (Mw=7.4) and 1999 November 12 Düzce (Mw=7.1) earthquakes in Turkey from teleseismic body waves using broad‐band data of the Global Seismograph Network, aftershock locations and mapped surface breaks. The centroid solutions indicate strike‐slip mechanisms for both events. The Izmit earthquake was characterized by rupture propagating predominantly eastwards. It consisted of a main rupture lasting about 25 s followed within 1 min by two more events of Mw=6.9 and Mw=7.0. With the teleseismic data, we could not resolve the westward extent of rupture into the Marmara Sea. However, an upper bound of the seismic moment release west of the epicentre of the Izmit event is estimated to be  1.9×1019 N m. The Düzce earthquake lasted about 14 s and was characterized by a bilateral mode of rupture, in excellent agreement with mapped surface breaks and aftershock locations.

S U M M A R YDifferential radar interferometry provided high-quality near-field deformation data for the 2003 Bam earthquake and therefore strong constraints on its source parameters. The ruptured fault segments could be clearly detected by using a Sobel Edge Filter on the phase-unwrapped deformation field. The estimated total rupture length is about 24 km. More than 80 per cent of the seismic moment was released from its southern segment of about 13 km, where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 MPa. In addition, optical remote sensing data show that the Bam fault is not a single fault but consists of a 4-5 km wide fault system with the known main branch running between the city of Bam and Baravat. The fault ruptured by the Bam earthquake appears to continue the NW branch of this fault system from Bam city southwards. Based on these results, we suggest that the Bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved.