The paper deals with the analysis of the propagation, heights, and arrival times of a tsunami that may occur on the coastal areas of Cyprus and Eastern Mediterranean in the case of an earthquake in ...southern Cyprus. Following a review of the seismic risk and historical earthquakes which occurred in southern Cyprus, it was concluded that this region may be subject to high vulnerability if a tsunami occurs. A study was conducted on the numerical modelling of a possible tsunami generated by movement along the fault of the 1222 Paphos earthquake. The region where the earthquake occurred can be attributed to the Cyprian Arc in the southwest of Cyprus. This arc is one of the most active seismic zones in the Mediterranean, which has led to the occurrence of earthquakes from submerged seismogenic sources. A methodology is used to simulate tsunami wave propagation for the Eastern Mediterranean coastal areas which requires the initial wave due to fault parameters as well as the bathymetry data. The GEBCO30 bathymetry data are used which have a grid spacing of 0.30 arc min. The fault parameters are deduced from the maximum stress directions and source geometry of the region from the moment tensor solutions derived from analyzing of earthquake waveforms. The numerical tsunami propagation model was performed by using SWAN code. The simulated highest tsunami heights were 4.02 m in Kouklia (Cyprus); 2.85 m in Paphos Ktima (Cyprus); 2.58 in Episkopi (Cyprus); 2.06 in Peyia (Cyprus); 1.76 in Yennadhi, Rhodes (Greece); 1.53 in Burg Migheizil (Egypt); 1.46 m in Tarabulus (Lebanon); 1.39 m in Bur Said (Egypt); 1.28 in Al-Burj (Egypt); and 0.60 in Muğla-Aksaz (Turkey). The results of the model outline the extent of the tsunami waves of damaging size, but destructive event in the region.
On 30 October 2020, a strong normal-faulting earthquake struck Samos Island in Greece and İzmir Province in Turkey, both in the eastern Aegean Sea. The earthquake generated a tsunami that hit the ...coasts of Samos Island, Greece and İzmir, Turkey. National teams performed two post-tsunami field surveys on 31 October to 1 November 2020, and 4–6 November 2020, along the Turkish coastline; while the former was a quick survey on the days following the tsunami, the latter involved more detailed measurement and investigation focusing on a ~ 110-km-long coastline extending from Alaçatı (Çeşme District of İzmir) to Gümüldür (Menderes District of İzmir). The survey teams measured runup and tsunami heights, flow depths, and inundation distances at more than 120 points at eight different localities. The largest tsunami runup among the surveyed locations was measured as 3.8 m in Akarca at a distance of 91 m from the shoreline. The maximum tsunami height of 2.3 m (with a flow depth of 1.4 m) was observed at Kaleiçi region in Sığacık, where the most severe tsunami damage was observed. There, the maximum runup height was measured as 1.9 m at the northeastern side of the bay. The survey team also investigated tsunami damage to coastal structures, noticing a gradual decrease in the impact from Gümüldür to further southeast. The findings of this field survey provide insights into the coastal impact of local tsunamis in the Aegean Sea.
Seismological observations provide essential input parameters for numerical tsunami simulations. Here, we present source mechanism parameters, finite-fault source rupture models and numerical tsunami ...simulation results for the destructive October 28, 2012 Haida Gwaii-Canada (
M
w
7.7) and September 16, 2015 Illapel-Chile (
M
w
8.3) earthquakes and resulting tsunamis. These two earthquakes were controlled by active tectonic features along the subduction zones that had developed in response to the convergent movements of lithospheric plates. The faulting geometry (strike, dip, and rake angles), focal depth, fault dimensions, average and maximum slip values on the fault planes and seismic moments of the earthquakes are estimated by analyzing teleseismic long-period P- and SH-waves and broadband P-waveforms and using waveform inversion and hybrid back-projection methods. The obtained slip models of the earthquakes reveal heterogeneous slip distributions on fault planes with long source durations (~ 80 s and 150 s) and low stress drop values (10–15 bars). Numerical simulations of tsunami wave propagation are further performed using the uniform and non-uniform slip models and nonlinear long-wave equations in spherical coordinates. The shape and arrival times of leading tsunami waves are adequately constrained particularly with the heterogeneous slip distribution models. The general characteristics of synthetic tsunami waveforms (e.g., amplitude, shape, arrival time) calculated using the non-uniform slip model, are more consistent with the observed tsunami records than those of a uniform slip model. It is further seen that simulation results using preliminary and fast slip models for both earthquakes give only approximate early tsunami estimates; tsunami wave heights and arrival times to the coasts are mostly not well simulated. The results indicate that tsunami simulations based on finite-fault source slip models likely contribute to the determination of tsunamigenic coastal regions by revealing locations, arrival times, amplitudes, and directions of tsunami waves within a close approximation to observed records off-shore and far from the source region. They provide sufficient information to facilitate tsunami warning and mitigation challenges after the destructive earthquakes. We further suggest that joint inversions of GPS, tsunami, teleseismic and strong ground motion records and higher resolution bathymetry data are needed in order to obtain better correlations between observed and synthetic tsunami data, especially for the later arriving waves.
► Testing the uniform and non-uniform slip models on tsunami propagation. ► The influence of slip heterogeneities on the wave amplitude in the near field. ► Comparing the simulated waves from ...proposed tsunami and seismic inversion studies. ► The impact of larger amount of slip at the trench site for the orientation of waves.
The numerical simulations of recent tsunami caused by 11 March 2011 off-shore Pacific coast of Tohoku–Oki earthquake (Mw 9.0) using diverse co-seismic source models have been performed. Co-seismic source models proposed by various observational agencies and scholars are further used to elucidate the effects of uniform and non-uniform slip models on tsunami generation and propagation stages. Non-linear shallow water equations are solved with a finite difference scheme, using a computational grid with different cell sizes over GEBCO30 bathymetry data. Overall results obtained and reported by various tsunami simulation models are compared together with the available real-time kinematic global positioning system (RTK-GPS) buoys, cabled deep ocean-bottom pressure gauges (OBPG), and Deep-ocean Assessment and Reporting of Tsunami (DART) buoys. The purpose of this study is to provide a brief overview of major differences between point-source and finite-fault methodologies on generation and simulation of tsunamis. Tests of the assumptions of uniform and non-uniform slip models designate that the average uniform slip models may be used for the tsunami simulations off-shore, and far from the source region. Nevertheless, the heterogeneities of the slip distribution within the fault plane are substantial for the wave amplitude in the near field which should be investigated further.
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•The rheology corresponds to the coupling in the west and the decoupling in the east.•The rheological stratification delineates the pattern of crustal seismic activities.•The present ...day rheology allows us to discuss principles of brittle-ductile systems.•The lower EET values are directly underlain by thinned lithosphere.
In this study, the regional components of global model EGM08 Bouguer anomalies obtained by low pass filtering were inverted to map the geometries of Moho and Lithosphere-Asthenosphere Boundary (LAB) of the central Anatolian region. It was determined the Moho and LAB depths in the region to be 35.8–41.2 km and 67–91 km, respectively. The results from rheological modeling indicate mechanical decoupling of the crust and uppermost lithospheric mantle in eastern part and coupling in the western part of the study area. We also compare the rheological stratification with the focal depth distribution of earthquakes to examine the possible discrepancies between the brittle-ductile transition zone and the maximum depths of earthquakes along the selected profiles. The spatial variations of effective elastic thicknesses (EET) of the lithosphere have been estimated from the strength of the crust and lithospheric mantle by implying deformation gradient at Moho and LAB. The EET values vary in the range of 19–24.3 km. Although the EET values are relatively high in the eastern part of the region, lower EET values are directly underlain by thinned lithosphere of northwestern and southwestern part of central Anatolian region. We also analyze the crustal rheologies obtained from the lithospheric strength by delineating the pattern of crustal seismic activities.
The 20th July 2017 Bodrum–Kos Tsunami Field Survey Dogan, Gozde Guney; Annunziato, Alessandro; Papadopoulos, Gerassimos A. ...
Pure and applied geophysics,
07/2019, Letnik:
176, Številka:
7
Journal Article
Recenzirano
The July 20, 2017 Bodrum–Kos Earthquake caused tsunami wave motions and damage in the south of Bodrum Peninsula, Turkey, and on Kos Island, Greece. Immediately after the earthquake, we conducted ...several post-tsunami field surveys including interviews in coastal zones impacted by the tsunami, i.e., the coastlines of Bodrum Peninsula, Karaada Islet and Akyaka Town in Gökova Bay, Turkey, and eastern Kos Island, Greece. We present observations and measurements to document the variation of the tsunami effects along the coast. The largest tsunami runup was about 1.9 m and observed at the mouth of a small dry streambed at Gumbet Bay, Bodrum. No significant water motions were reported at the northern and western coasts of Bodrum Peninsula. The tsunami runup distribution along the coast of eastern Kos was overall regular, with runup not exceeding 1 m except in the Port of Kos where a 1.5 m tsunami runup was measured.
The city of Adapazarı — located in the Marmara Region of northwest Turkey — is situated on a deep sedimentary basin and was the city most heavily damaged by the strong ground motion of the 17 August ...1999 Kocaeli earthquake (moment magnitude M
w
= 7.4). This study determines site amplifications of the attenuation relationships for shallow earthquakes in the Adapazarı basin by using the previous ground motion prediction equations (GMPEs) and the traditional spectral ratio method. The site amplifications are determined empirically by averaging the residuals between the observed and predicted peak ground acceleration (PGA) and spectral acceleration (SA) values for various periods. Residuals are significantly correlated with the known characteristics of geological units. A new attenuation model has also been developed for 5% damped spectral acceleration to determine the dependence of strong ground motions on frequency.
Site amplification was evaluated at ten stations located in the Adapazarı basin. The PGA site amplification values varied between 1.130 and 3.120 in all stations except two; these exceptions resulted in de-amplifications. Calculated de-amplification values of these stations indicate a consistency for rock medium. The site amplification values of some stations indicate an increase while moving away from the surface rupture and approaching the contact between the alluvial deposits and bedrock. One station, located on the discontinuity between the two different media, has the highest site amplification value (3.12) in the study area. This high value might be a result of the focusing of the seismic waves due to the discontinuities located on both sides of the narrow basin.
The traditional spectral ratio method was also used to determine amplification in the Adapazarı basin. One station on bedrock was chosen as a reference station. When the results of this method are evaluated, the amplifications at high periods are attributed to the thick sedimentary deposits in the basin and the apparent de-amplifications at low periods are partly due to the reference site response.
When the spectral ratios or spectral residuals of the stations located on alluvial deposits or soft soils are considered, it is observed that these stations have high spectral ratio or residual values, especially at high periods. The source of these high period amplifications may be the geometry of the basin, the presence of soft-loose soil levels and high period basin-transduced surface waves.
Amplification and predominant periods of soils in Düzce Basin were investigated by analysing the data sets of last two major earthquakes and aftershocks of Kocaeli and Düzce earthquakes occurred in ...1999 with a magnitude of Mw:7.4 and Mw:7.2, respectively. Two different methods named horizontal/vertical spectral acceleration ratio (HVSAR) and soil-to-rock Response Spectral Acceleration Ratio (RSAR) were used to determine soil amplifications for various periods in Düzce Basin. The data set includes 31 strong gorund motion records from five strong ground motion stations. It was found that the site amplifications at stations are directly related to the local geology underlying the stations. Averaging the residuals between the predicted and observed PGAs resulted in soil amplification from 1.33 to 2.33. The HVSAR method presented soil amplification values between 2.7 and 10 and predominant period values between 0.4 and 0.7 s. Soil amplification values from 1.5 to 14 and predominant periods from 0.5 to 0.8 s were obtained by the RSAR method. High site amplifications and predominant periods mainly depend on the thickness of lithological variances accompanied by low physical and geotechnical properties of alluvial deposits.
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