Analysis of October 23 (Mw 7.2) and November 9 (Mw 5.6), 2011 Van Earthquakes Using Long-Term GNSS Time Series

The eastern Anatolia provides one of the best examples of an area of rapid deformation and intense contraction that is the consequence of an active continental collision between the Arabian and Eurasian plates leading to large and devastating earthquakes. The latest evidence of the active tectonism in the region is revealed by two remarkable seismic events; Van-Tabanli (Mw 7.2, October 23, 2011) and Van-Edremit (Mw 5.6, November 9, 2011) earthquakes. The study of the earthquake cycle and observation of geodetic and seismic deformation in this region is very important to hazard assessments. In this study, the inter-seismic, co-seismic, and post-seismic movements caused by the above-mentioned earthquakes were investigated using the time series of 2300 days of Global Navigation Satellite Systems (GNSS) observations of the local stations selected from the network of the Continuously Operating Reference Stations, Turkey (CORS-TR). For the inter-seismic period, approximately 1100 daily data were obtained from 21 CORS-TR stations (prior to the earthquakes between October 1, 2008 and October 23, 2011) and evaluated using the GAMIT/GLOBK software. The behaviour of these stations was investigated by processing 1 Hz data from the GNSS stations during the earthquakes on the GAMIT/TRACK software. In addition to October 23 and November 9, the GNSS data on one day before and after the earthquakes was assessed to determine co-seismic deformations. During the October 23 earthquake, hanging-wall deformation of about 60 mm was detected in the SW direction at the MURA station. However, at the VAAN station, deformation of 200 mm (value predicted by time series) was observed in the footwall block in the NW direction. There were not any significant changes at the stations during the November 9 earthquake. For the post-seismic period, the GNSS data from 2012 to 2015 was evaluated. According to the observations, post-seismic deformation continued at the stations close to the epicenter of the earthquake.Anatolia oriental provee uno de los mejores ejemplos de un área de rápida deformación e intensa contracción, consecuencia de una colisión continental activa entre la placa Arábiga y la Euroasiática, lo que causa grandes y devastadores terremotos. Dos notables terremotos son evidencia de la actividad tectónica de la región: los terremotos Van-Tabanli (7.2 Mw. 23 de octubre de 2011) y Van-Edremit (5.6 Mw, 9 de noviembre de 2011). El estudio del ciclo sísmico y la observación de las deformaciones geodésicas y sísmicas en esta región es fundamental para la evaluación de riesgo. En este estudio, se investiga las fases inter-, co- y post-sísmicas asociados a estos terremotos a través de 2300 días de observaciones del Sistema Global de Navegación por Satélite (GNSS, por sus siglas en inglés) de estaciones locales seleccionadas de la red de Estaciones de Referencia de Funcionamiento Continuo en Turquía (CORS-TR). Para el periodo intersísmico se obtuvieron aproximadamente 1100 datos diarios de 21 estaciones CORS-TR (anteriores a los terremotos entre el 1 de octubre de 2008 y el 23 de octubre de 2011) y evaluados con el software GAMIT/GBLOK. El comportamiento co-sísmico fue investigado procesando datos de 1 Hz de las estaciones GNSS durante los terremotos en el software GAMIT/TRACK. Adicionalmente se evaluaron datos del GNSS un día antes y un día después de los terremotos para determinar las deformaciones cosísmicas. Durante el terremoto del 23 de octubre, en el bloque colgante se detectó una deformación de 60 mm en dirección SW (estación MURA). En la estación VAAN en el bloque yacente se observó una deformación de 200 mm en dirección NW (valor predicho por series temporales). Durtante el terremoto del 9 de Noviembre no se observó cambios significativos. Para la fase post-sísmica se evaluaron los datos de la GNSS del 2012 al 2015. Según las observaciones, la deformación postsísmica continuó en las estaciones cercanas al epicentro del terremoto

Aktivna deformacija Zemljine površine utvrđena preciznim nivelmanskim premjerom u Afyon-Akşehir grabenu u Zapadnoj Anadoliji u Turskoj

In the actively deforming region of western Anatolia, crustal deformation is accommodated by destructive earthquakes and a variety of aseismic events. In this study, we investigated the 2016–2017 aseismic sequence located in the Bolvadin Fault, one of the segments of the Akşehir-Simav Fault System of western Anatolia by analysing surface deformation derived from detailed geological mapping. Our findings suggest that surface deformation in the Bolvadin Fault is accommodated by aseismic episodes. During the field studies in the Bolvadin area, progressive surface deformations, such as surface faults and earth fissures with a length of 800 meters to 3 kilometres and strike of N15°E to N70°E were mapped on a 1/5000 scale. Furthermore, a levelling network was established to calculate the vertical displacements and deformation rate along the surface deformations. Precision level measurements were undertaken in 2016 and 2017. On the routes to the NW of the Bolvadin settlement, a vertical deformation rate of 30 mm/yr was detected in the period of 2016–2017, and a large deformation rate of 40 mm/yr was detected in the same period.Aktivna deformacija Zemljine kore se u regiji Zapadne Anadolije kompenzira razornim potresima i drugim seizmičkim događajima. U ovom smo radu na temelju detaljnog geološkog kartiranja analizirali deformaciju površine kako bismo proučili niza seizmičkih događaja u razdoblju 2016.–2017. na lokaciji rasjeda Bolvadin, jednoga od segmenata rasjednoga sustava Akşehir-Simav u Zapadnoj Anadoliji. Naši rezultati ukazuju na to da se površinska deformacije kompenzira tijekom aseizmičkih epizoda. Tijekom terenskih istraživanja u području Bolvadin, progresivne su površinske deformacije, poput površinskih rasjeda ili pukotina duljina od 800 m do 3 km, pružanja N15°E do N70°E, kartirane u mjerilu 1:5 000. Nadalje, uspostavljena je nivelmanska mreža kako bi se izmjerila brzina pomaka i deformacija. Precizna nivelmanska mjerenja izvedena su 2016. i 2017. godine. Na pravcima usmjerenima SZ od naselja Bolvadin, ustanovljena je brzina vertikalne deformacije od 30 mm/god., a u istom je razdoblju izmjerena i velika brzina deformacije od 40 mm/god

Tectonic geomorphology of the Spildagi High Ranges, western Anatolia

The Spildagi High Ranges represent the footwall block of the Manisa Fault Zone (MFZ), which is one of the NW-SE to E-W-trending active dip-slip normal fault systems in western Anatolia. The Spildagi High Ranges were uplifted by approximately 1500 m with respect to the lowland Manisa Basin following the Late Miocene. The Plio-Quaternary active tectonics was interpreted through a detailed geomorphic study of the fault-generated mountain fronts and drainage pattern of the Spildagi High Ranges. The combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity along the MFZ. Morphometric measures such as axial river profiles, drainage basin geometry, triangular facets, and mountain-front lineament patterns document the impact of active tectonics on the landscape evolution of the MFZ, which resulted in the subdivision of western, central, and eastern sectors. An axial river, flowing in the Manisa Basin, is represented by the Gediz River that exhibits a meandering-braided transition pattern. The relative positions of the palaeochannels and oxbows evidence the south-westward migration of the Gediz River towards the MFZ. We infer that the source of axial river migration is tilting of the Manisa plain due the listric nature of the MFZ. Quantitative measurement of geomorphic indices such as mountain-front sinuosity (S-mf; 1.11-1.14), valley floor width-to-height ratios (V-f; 0.033 0.947), facet heights (25-1060 m), and facet slopes (5.77 degrees-40.21 degrees) suggest a relatively high degree of tectonic activity along the MFZ. Hypsometric curves for all sector slopes mostly exhibit straight or concave shapes, indicating the presence of the young and weakly eroded mountain front of the Spildagi High Ranges. The combined geomorphic indices and field data suggest that the analysed dip-slip normal fault segments are linear and highly active. (C) 2012 Elsevier B.V. All rights reserved

Neogene-Quaternary evolution of the Manisa Basin: Evidence for variation in the stress pattern of the Izmir-Balikesir Transfer Zone, western Anatolia

In this paper, we aim to identify the Neogene-Quaternary evolution of the Manisa Basin located in the Izmir-Balikesir Transfer Zone (IBTZ) which lies between the normal-fault-dominated West Anatolian Extensional Province (WAEP) and the strike-slip-dominated North Aegean Region (NAR). The Manisa Basin, which forms a connection with the Gediz Graben, underwent two-stage basin evolution, distinguished by an ancient and modern graben-fill. The ancient basin-fill is made up of a folded and normal-to-reverse faulted and strike-slip-faulted Miocene volcano-sedimentary sequence. The younger modern basin-fill is represented by the Quaternary Bahadir Formation comprising fluvial terrace deposits, early-middle Pleistocene continental clastics of the Turgutlu Formation, alluvial/colluvial sediments of late Pleistocene-early Holocene Emlakdere Formation, and Holocene alluvium

Neotectonic Evolution of an Actively Growing Superimposed Basin in Western Anatolia: The Inner Bay of Izmir, Turkey

Izmir Bay is an actively growing shallow marine basin controlled by active faults trending NE, NW, N-S and E-W, in the West Anatolian Extensional Province. The bay of Izmir is a lazy L-shaped superimposed basin which is topographically divided into an E-W-trending inner bay and a NW-trending outer bay. The Inner Bay of Izmir is an asymmetric graben structure approximately 5-7 km wide and 25 km long containing (i) upper Cretaceous-Palaeocene basement, (ii) an older succession of lower to upper Miocene basin fill, overlain with angular unconformity by (iii) a younger Plio-Quaternary basin fill. The older succession contain a 0.5- to 1.5-km-thick, folded and coal-bearing continental volcano-sedimentary sequence. The younger succession of the Inner Bay of Izmir includes the upper Pliocene-Pleistocene Gorece formation and Holocene to recent alluvial fan, fan delta to shallow marine deposits

Geological and Palaeoseismological Evidence for Late Pleistocene-Holocene Activity on the Manisa Fault Zone, Western Anatolia

In West Anatolia near the cities of Izmir and Manisa, the historical occurrence of large earthquakes suggests the presence of important seismogenic faults. However, these faults have yet to be investigated in detail. The Manisa Fault Zone (MFZ) is an active large-scale normal fault system in this area, and thus field observations and palaeoseismological studies of this zone are important for predicting future earthquakes. Hence we sought to document geological and palaeoseismological evidence for Holocene activity on the MFZ. We performed trenching to determine the magnitude and timing of past surface-faulting events using detailed fault-trace mapping, measurements of Upper Pleistocene-Lower Holocene sediments, and radiocarbon dating. By comparing the trench data with palaeoearthquake records, we find evidence for three palaeoearthquakes which correspond to 926 AD, 1595 or 1664 AD, with the most recent event in 1845 AD. We also find this in the central and western sectors of the MFZ, which together with the eastern sector comprise the three major seismogenic zones. The Pliocene-Quaternary vertical off set at fault scarps is far less than that in the western sector, suggesting that activities of these sectors are highly independent. Evaluation of field observations suggests that the MFZ has been the source of multiple Late Pleistocene and Holocene surface-rupturing earthquakes. Our results constitute the first palaeoseismic evidence on the causative faults of historical earthquakes that affected Manisa, and point to their underlying tectonic mechanisms

Structural evidence for strike-slip deformation in the Izmir-Balikesir transfer zone and consequences for late Cenozoic evolution of western Anatolia (Turkey)

The Izmir-Balikesir transfer zone (IBTZ) is a recently recognized strike-slip dominated shear zone that accommodates the differential deformation between the Cycladic and Menderes core complexes within the Aegean Extensional System. Here, we present new structural and kinematic data obtained from field observations and 1/25,000 scale mapping of Miocene to Recent units within the IBTZ around Izmir Bay. The results point out that the IBTZ is a transtensional brittle shear zone that affects the pre-Neogene basement rock units, the early-middle Miocene volcano-sedimentary units and the Plio-Quaternary continental units

Geodetic evidence for aseismic fault movement on the eastern segment of the Gediz Graben system (western Anatolia extensional province, Turkey) and its significance for settlements

Aseismic dip-slip normal fault displacement related to numerous fast-slipping active faults was recently observed in several localities in the western Anatolia extensional province. Still, the characteristics of displacements along with the behavior of individual fault segments are poorly known. Here we analyze an aseismically active normal fault affecting the settlement area of the Sarigol district, Turkey, at the surface rupture area of the 1969 magnitude 6.5 Alasehir earthquake. A precise leveling method was implemented in this area between July 2017 and 2020, to determine the vertical movements of the hanging wall relative to the footwall of the Sarigol fault. The yearly vertical movement on the surface along Profile 1 was - 7.0, - 7.3, and - 7.0 cm, respectively, for the three years starting in July 2017, and on Profile 2 it was - 7.7, - 8.7, and - 7.8 cm for the same time period. This persistent deformation, especially in the summer and fall seasons, suggests that may be related to groundwater level changes. Intensive agriculture is conducted in the region and a high level of irrigation activity in the summer period causes a decrease in groundwater levels. In addition, the continued deformation together with intensive precipitation in winter and spring despite high groundwater levels leads to the idea that tectonic creep movement could be a second reason for the deformation in the area. In the current study, the most important result is that the aseismic deformation starting after the 1969 Mw6.5 Alasehir earthquake still continues rapidly today with a velocity of 70-80 mm/year down-dip. This indicates that the damage zone of the Sarigol fault is not appropriate for settlements in the Sarigol district due to continuous high amounts of vertical displacement, and that appropriate building policy and awareness campaigns are needed

Análisis de los terremotos de octubre 23 (7.2 Mw) y noviembre 9 (5.6 Mw) de 2011 en Van a través de series temporales GNSS a largo plazo

The eastern Anatolia provides one of the best examples of an area of rapid deformation and intense contraction that is the consequence of an active continental collision between the Arabian and Eurasian plates leading to large and devastating earthquakes. The latest evidence of the active tectonism in the region is revealed by two remarkable seismic events; Van-Tabanli (Mw 7.2, October 23, 2011) and Van-Edremit (Mw 5.6, November 9, 2011) earthquakes. The study of the earthquake cycle and observation of geodetic and seismic deformation in this region is very important to hazard assessments. In this study, the inter-seismic, co-seismic, and post-seismic movements caused by the above-mentioned earthquakes were investigated using the time series of 2300 days of Global Navigation Satellite Systems (GNSS) observations of the local stations selected from the network of the Continuously Operating Reference Stations, Turkey (CORS-TR). For the inter-seismic period, approximately 1100 daily data were obtained from 21 CORS-TR stations (prior to the earthquakes between October 1, 2008 and October 23, 2011) and evaluated using the GAMIT/GLOBK software. The behaviour of these stations was investigated by processing 1 Hz data from the GNSS stations during the earthquakes on the GAMIT/TRACK software. In addition to October 23 and November 9, the GNSS data on one day before and after the earthquakes was assessed to determine co-seismic deformations. During the October 23 earthquake, hanging-wall deformation of about 60 mm was detected in the SW direction at the MURA station. However, at the VAAN station, deformation of 200 mm (value predicted by time series) was observed in the footwall block in the NW direction. There were not any significant changes at the stations during the November 9 earthquake. For the post-seismic period, the GNSS data from 2012 to 2015 was evaluated. According to the observations, post-seismic deformation continued at the stations close to the epicenter of the earthquake.Anatolia oriental provee uno de los mejores ejemplos de un área de rápida deformación e intensa contracción, consecuencia de una colisión continental activa entre la placa Arábiga y la Euroasiática, lo que causa grandes y devastadores terremotos. Dos notables terremotos son evidencia de la actividad tectónica de la región: los terremotos Van-Tabanli (7.2 Mw. 23 de octubre de 2011) y Van-Edremit (5.6 Mw, 9 de noviembre de 2011). El estudio del ciclo sísmico y la observación de las deformaciones geodésicas y sísmicas en esta región es fundamental para la evaluación de riesgo. En este estudio, se investiga las fases inter-, co- y post-sísmicas asociados a estos terremotos a través de 2300 días de observaciones del Sistema Global de Navegación por Satélite (GNSS, por sus siglas en inglés) de estaciones locales seleccionadas de la red de Estaciones de Referencia de Funcionamiento Continuo en Turquía (CORS-TR). Para el periodo intersísmico se obtuvieron aproximadamente 1100 datos diarios de 21 estaciones CORS-TR (anteriores a los terremotos entre el 1 de octubre de 2008 y el 23 de octubre de 2011) y evaluados con el software GAMIT/GBLOK. El comportamiento co-sísmico fue investigado procesando datos de 1 Hz de las estaciones GNSS durante los terremotos en el software GAMIT/TRACK. Adicionalmente se evaluaron datos del GNSS un día antes y un día después de los terremotos para determinar las deformaciones cosísmicas. Durante el terremoto del 23 de octubre, en el bloque colgante se detectó una deformación de 60 mm en dirección SW (estación MURA). En la estación VAAN en el bloque yacente se observó una deformación de 200 mm en dirección NW (valor predicho por series temporales). Durtante el terremoto del 9 de Noviembre no se observó cambios significativos. Para la fase post-sísmica se evaluaron los datos de la GNSS del 2012 al 2015. Según las observaciones, la deformación postsísmica continuó en las estaciones cercanas al epicentro del terremoto