TY - JOUR A1 - Jamalreyhani, Mohammadreza A1 - Rezapour, Mehdi A1 - Cesca, Simone A1 - Dahm, Torsten A1 - Heimann, Sebastian A1 - Sudhaus, Henriette A1 - Isken, Marius Paul T1 - Insight into the 2017-2019 Lurestan arc seismic sequence (Zagros, Iran); complex earthquake interaction in the basement and sediments JF - Geophysical journal international N2 - Despite its high-seismogenic potential, the details of the seismogenic processes of Zagros Simply Folded Belt (SFB) remains debated. Three large earthquakes (M-w 7.3, 5.9 and 6.3) struck in the Lurestan arc of the Zagros SFB in 2017 and 2018. The sequence was recorded by seismic stations at regional, and teleseismic distances. Coseismic surface displacements, measured by Sentinel-1A/B satellites, provide additional data and a unique opportunity to study these earthquakes in detail. Here, we complement previous studies of the coseismic slip distribution of the 12 November 2017 M-w 7.3 Ezgeleh earthquake by a detailed analysis of its aftershocks, and we analysed the rupture process of the two interrelated earthquakes (25 August 2018 M-w 5.9 Tazehabad and the 25 November 2018 M-w 6.3 Sarpol-e Zahab earthquakes). We model the surface displacements obtained from Interferometric Synthetic Aperture Radar (InSAR) measurements and seismic records. We conduct non-linear probabilistic optimizations based on joint InSAR and seismic data to obtain finite-fault rupture of these earthquakes. The Lurestan arc earthquakes were followed by a sustained aftershock activity, with 133 aftershocks exceeding M-n 4.0 until 30 December 2019. We rely on the permanent seismic networks of Iran and Iraq to relocate similar to 700 M-n 3 + events and estimate moment tensor solutions for 85 aftershocks down to M-w 4.0. The 2017 Ezgeleh earthquake has been considered to activate a low-angle (similar to 17 degrees) dextral-thrust fault at the depth of 10-20 km. However, most of its aftershocks have shallow centroid depths (8-12 km). The joint interpretation of finite source models, moment tensor and hypocentral location indicate that the 2018 Tazehabad and Sarpol-e Zahab earthquakes ruptured different strike-slip structures, providing evidence for the activation of the sinistral and dextral strike-slip faults, respectively. The deformation in the Lurestan arc is seismically accommodated by a complex fault system involving both thrust and strike-slip faults. Knowledge about the deformation characteristics is important for the understanding of crustal shortening, faulting and hazard and risk assessment in this region. KW - Joint Inversion KW - Waveform inversion KW - Earthquake source observations KW - Seismicity and tectonics Y1 - 2022 U6 - https://doi.org/10.1093/gji/ggac057 SN - 0956-540X SN - 1365-246X VL - 230 IS - 1 SP - 114 EP - 130 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Kulikova, Galina A1 - Schurr, Bernd A1 - Krüger, Frank A1 - Brzoska, Elisabeth A1 - Heimann, Sebastian T1 - Source parameters of the Sarez-Pamir earthquake of 1911 February 18 JF - Geophysical journal international N2 - The Ms ∼ 7.7 Sarez-Pamir earthquake of 1911 February 18 is the largest instrumentally recorded earthquake in the Pamir region. It triggered one of the largest landslides of the past century, building a giant natural dam and forming Lake Sarez. As for many strong earthquakes from that time, information about source parameters of the Sarez-Pamir earthquake is limited due to the sparse observations. Here, we present the analysis of analogue seismic records of the Sarez-Pamir earthquake. We have collected, scanned and digitized 26 seismic records from 13 stations worldwide to relocate the epicentre and determine the event's depth (∼26 km) and magnitude (mB7.3 and Ms7.7). The unusually good quality of the digitized waveforms allowed their modelling, revealing an NE-striking sinistral strike-slip focal mechanism in accordance with regional tectonics. The shallow depth and magnitude (Mw7.3) of the earthquake were confirmed. Additionally, we investigated the possible contribution of the landslide to the waveforms and present an alternative source model assuming the landslide and earthquake occurred in close sequence. KW - Earthquake source observations KW - Seismicity and tectonics KW - Body waves KW - Theoretical seismology Y1 - 2016 U6 - https://doi.org/10.1093/gji/ggw069 SN - 0956-540X SN - 1365-246X VL - 205 SP - 1086 EP - 1098 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Nooshiri, Nima A1 - Saul, Joachim A1 - Heimann, Sebastian A1 - Tilmann, Frederik A1 - Dahm, Torsten T1 - Revision of earthquake hypocentre locations in global bulletin data sets using source-specific station terms JF - Geophysical journal international N2 - Global earthquake locations are often associated with very large systematic travel-time residuals even for clear arrivals, especially for regional and near-regional stations in subduction zones because of their strongly heterogeneous velocity structure. Travel-time corrections can drastically reduce travel-time residuals at regional stations and, in consequence, improve the relative location accuracy. We have extended the shrinking-box source-specific station terms technique to regional and teleseismic distances and adopted the algorithm for probabilistic, nonlinear, global-search location. We evaluated the potential of the method to compute precise relative hypocentre locations on a global scale. The method has been applied to two specific test regions using existing P- and pP-phase picks. The first data set consists of 3103 events along the Chilean margin and the second one comprises 1680 earthquakes in the Tonga-Fiji subduction zone. Pick data were obtained from the GEOFON earthquake bulletin, produced using data from all available, global station networks. A set of timing corrections varying as a function of source position was calculated for each seismic station. In this way, we could correct the systematic errors introduced into the locations by the inaccuracies in the assumed velocity structure without explicitly solving for a velocity model. Residual statistics show that the median absolute deviation of the travel-time residuals is reduced by 40-60 per cent at regional distances, where the velocity anomalies are strong. Moreover, the spread of the travel-time residuals decreased by similar to 20 per cent at teleseismic distances (>28 degrees). Furthermore, strong variations in initial residuals as a function of recording distance are smoothed out in the final residuals. The relocated catalogues exhibit less scattered locations in depth and sharper images of the seismicity associated with the subducting slabs. Comparison with a high-resolution local catalogue reveals that our relocation process significantly improves the hypocentre locations compared to standard locations. KW - Seismicity and tectonics KW - Computational seismology KW - Subduction zone processes KW - Pacific Ocean KW - South America Y1 - 2016 U6 - https://doi.org/10.1093/gji/ggw405 SN - 0956-540X SN - 1365-246X VL - 208 IS - 2 SP - 589 EP - 602 PB - Oxford Univ. Press CY - Oxford ER -