Lg Coda Variations in North-Central Iran

Ground motion records in north-central Iran have been used in order to obtain the Lg coda Q, using stack spectral ratio method. The lateral variations in Q 0 and its frequency dependence are estimated in the 0.3-7.0 Hz frequency range which led to Q = 267(±32) × f 0.71(±0.14) . The observed variations in quality factor show low values of Q 0 in western part of the study region where bounded by relatively high values in southern and northern parts. Since the seismicity of the study area is quite shallow the obtained results can be attributed to the upper 30 km of the crust. The Damavand volcano and its surrounding region also exhibit variations in the value of Q 0 which result in low and intermediate values of Q 0 in western and eastern parts, respectively. Current seismicity in Damavand is mostly confined to its southwestern part, whereas our results proved to possess low values of Q 0 . In general, most of Q factor variations can be attributed to the lateral heterogeneity as well as the severity of the crustal velocity gradient, and as expected the north-central Iran is well inferred as a tectonically active region

Feasibility study of earthquake early warning in Tehran, Iran

In this study, we examine the scientific feasibility of an Earthquake Early Warning System in Tehran, Iran, by the integration of the Tehran Disaster Mitigation and Management Organization (TDMMO) accelerometric network and the PRobabilistic and Evolutionary early warning SysTem (PRESTo). To evaluate the performance of the TDMMO-PRESTo system in providing the reliable estimations of earthquake parameters and the available lead-times for The Metropolis of Tehran, two different approaches were analyzed in this work. The first approach was assessed by applying the PRESTo algorithms on waveforms from 11 moderate instrumental earthquakes that occurred in the vicinity of Tehran during the period 2009-2020. Moreover, we conducted a simulation analysis using synthetic waveforms of 10 large historical earthquakes that occurred in the vicinity of Tehran. We demonstrated that the six worst-case earthquake scenarios can be considered for The Metropolis of Tehran, which are mostly related to the historical and instrumental events that occurred in the southern, eastern, and western parts of Tehran. Our results indicate that the TDMMO-PRESTo system could provide reliable and sufficient lead-times of about 1 to 15s and maximum lead-times of about 20s for civil protection purposes in The Metropolis of Tehran

Dynamics of European Cultural Diplomacy in India: The Case study of Alliance Françoise de Bangalore

Kultūras diplomātija ieņem galveno vietu daudzu valstu ārpolitikā. Kultūras diplomātijas pētnieciskā literatūra ir attīstījusies, iekļaujot izmaiņas tās praksē tādas kā sadarbība, jaunu aktieru iesaiste, jauni kanāli, caur kuriem sadarbību praktizē, un sasniedz jaunus mērķus. Darba mērķis ir veicināt kultūras un publiskās diplomātijas lauciņu, analizējot Eiropas kultūras diplomātijas dinamiku caur trešās pasaules valstīm. Darbs pēta Franču alianses darbību Bengalūru, Indijā, izmantojot gadījuma analīzes metodi. Darbs koncentrējās uz visu valodas apgūšanas sistēmu kultūras institūtos, aplūkojot to kā kultūras un publiskās diplomātijas ziņu pavairotāju. Dati tika vākti un analizēti, balstoties uz trīs “A” modeli, kas iekļauj apzināšanos, novērtēšanu un pievilcību pret Franciju, tās kultūru, Eiropu un Eiropas Savienību. Starp valodu apguvējiem tika veikta aptauja, kuras rezultāti parādīja statistiski nozīmīgu atšķirību starp valodas apguvēju apzināšanās līmeņiem un novērtēšanas līmeņiem pret Franciju un tās kultūru un apzināšanās, un pievilcības līmeņiem pret Eiropu un Eiropas Savienību. Tādēļ darbā tiek pētīts valodas un kultūras sapīšanās savā būtībā un valodas apgūšanas procesā rezultējošo valodas apguvēju pakļaušanos kādas tautas kultūrai. Darbā tiek apgalvots, ka Eiropas Savienības dalībvalstu kultūras institūti papildina Eiropas Savienības publiskās diplomātijas pūles, tās maigo varu, tajā pašā laikā darbojoties iekš ierobežotās nacionālās publiskās diplomātijas sfērās. Valodu apmācība kultūras institūtos tiek skatīta kā socializācijas un nemitīgas iepazīšanas process un kultūras institūts pats par sevi tiek skatīts kā socializācijas punkts.With cultural diplomacy taking the central stage in the foreign policies of many nations, the scholarship on it has also risen to include the changes in its practice as two way street, the entry of new actors, new channels through which it is practiced and the fulfillment of new goals. This thesis aims at contributing to the field of cultural and public diplomacy by analyzing the dynamics of European cultural diplomacy practices through cultural institutes in third countries. Using the case study method, the thesis studies the activities of Alliance Française in Bangalore, India. The thesis focuses on the entire system of language learning at cultural institutes, viewing it as a cultural and public diplomacy message multiplier. Data were collected and analyzed based on a Triple-A model of awareness, appreciation and attraction towards France, its culture, Europe and the EU. Results from a survey conducted among the language learners reveals a statistically significant difference between the levels of language learners in the awareness and appreciation levels towards France and its culture and in the awareness and attraction levels towards Europe and the EU. Thus the thesis explores the intertwining of language and culture in their being and the resulting exposure of the language learners to the culture of a nation in the process of learning the language. The thesis contends that the cultural institutes of European Union member countries complement the EU’s public diplomacy efforts, thereby its soft power, whilst acting within circumscribed spheres of national public diplomacy. Language learning at cultural institutes is viewed as socialization and a continual familiarization process and the cultural institute itself as the loci of socialization

Lg Coda Variations in North-Central Iran

Ground motion records in north-central Iran have been used in order to obtain the Lg coda Q, using stack spectral ratiomethod. The lateral variations in Q0 and its frequency dependence are estimated in the 0.3–7.0Hz frequency range which ledto Q = 267(±32) × f 0.71(±0.14). The observed variations in quality factor show low values of Q0 in western part of the study regionwhere bounded by relatively high values in southern and northern parts. Since the seismicity of the study area is quite shallowthe obtained results can be attributed to the upper 30 km of the crust. The Damavand volcano and its surrounding region alsoexhibit variations in the value of Q0 which result in low and intermediate values of Q0 in western and eastern parts, respectively.Current seismicity in Damavand is mostly confined to its southwestern part, whereas our results proved to possess low values of Q0. In general, most of Q factor variations can be attributed to the lateral heterogeneity as well as the severity of the crustal velocitygradient, and as expected the north-central Iran is well inferred as a tectonically active region

On the strength of the phase cross-correlation in retrieving the Green's function information in a region affected by persistent aftershock sequences

Although research on seismic interferometry is now entering a phase of maturity, earthquakes are still the most troublesome issues that plague the process in real applications. To address the problems that arise from spatially scattered and temporally transient enormous earthquakes, preference is usually given to the use of time-dependent weights. However, small earthquakes can also have a disturbing effect on the accuracy of interpretations if they are persistently clustered right next to the perpendicular bisector of the line joining station pairs or in close proximity to one of the stations. With regard to the suppression of these cluster earthquakes, commonly used solutions for dealing with monochromatic microseismic cluster events (e.g., implementing a band-reject filter around a comparatively narrow frequency band or whitening the amplitude spectra before calculating the cross-spectrum between two signals) may not have the necessary efficiency since earthquake clusters are generally a collection of events with different magnitudes, each having its own frequency and energy contents. Therefore, the only solution left in such a situation is to use stronger non-linear time-dependent weights (e.g., square of the running average or one-bit normalization), which may cause Green's function amplitude information to be lost. In this paper, by simulating the records of a benchmark earthquake M-N 5.2 with the help of empirical Green's functions (EGF) obtained after the Ahar-Varzeghan Earthquake Doublet (M-N 6.4 and M-N 6.3), it is shown that the amplitude-unbiased phase cross-correlation is a relatively efficient approach in the face of the issues concerning long-standing cluster events

3-D body-wave tomography from the seismic ambient noise recorded by a dense array in the Dehdasht area, Iran

International audienceThe strong attenuation of the thick sedimentary layers in the Dehdasht region, Iran, renders active seismic exploration surveys difficult. The imaging of the existent limestone reservoirs is limited to the shallow subsurface due to the strong attenuation of seismic waves. Here, we discuss a different approach to imaging the subsurface using body waves extracted from the cross-correlation of the seismic ambient wavefield. We discuss the technical challenges to extracting clear P-wave arrivals from the seismic ambient wavefield of a dense 3-component seismic array deployed in the Dehdasht basin. We invert the data for the 3-D P-wave velocity structure and compare the velocity model with results from the 2-D active seismic surveys in the area. The results show the potential of using body waves extracted from the seismic ambient wavefield for imaging purposes in highly attenuating areas

3D joint inversion of gravity data and Rayleigh wave group velocities to resolve shear-wave velocity and density structure in the Makran subduction zone, south-east Iran

International audienceIn this study, we developed a method to invert jointly Rayleigh wave group velocities and gravity anomalies for velocity and density structure of the lithosphere. We applied the method to the Makran accretionary prism, SE Iran. The reason for using different data sets is that each of these data sets is sensitive to different parameters. Surface wave group velocities are sensitive mainly to shear wave velocity distribution in depth but do not well resolve density variations. Therefore, joint inversion with gravity data increases the resolution of density distribution. Our approach differs from others mainly in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for the properties of only four layers: thickness, P- and S-wave velocities and densities and their vertical gradients in sediments, upper-crust, lower-crust and upper mantle. The method is applied first to synthetic models in order to demonstrate its usefulness. We then applied the method to real data to investigate the lithosphere structure beneath the Makran. The resulting model shows that Moho depth increases from Oman Sea (18–33 km) and Makran fore-arc (33–37 km) to the volcanic-arc (44–46 km). The crustal density is high in the Oman Sea as should be expected for the oceanic crust. We also find a high-velocity anomaly in the upper mantle under the Oman Sea corresponding to the subducting slab. The crust under the fore-arc, volcanic-arc and back-arc settings of Makran subduction zone is characterized by low-velocity zones

Integrated analysis of surface wave velocity and gravity data for the development of new density-velocity models of the crust and upper mantle in SE Iran

International audienceInversion of Rayleigh wave dispersion curves is challenging due to its nonlinearity and multimodality. In this paper, a Simulated Annealing (SA) algorithm is applied to the nonlinear inversion of fundamental-mode Rayleigh wave group dispersion curves for shear and compressional wave velocities. In our approach, we invert thickness, velocities and densities and their vertical gradients of four layers, sediments, upper-crust, lower-crust and lithospheric mantle. At first, to determine the efficiency and stability of the method, noise-free and noisy synthetic data sets are inverted. Results from the synthetic data demonstrate that the SA applied to the nonlinear inversion of surface wave data is interesting not only in terms of accuracy but also in terms of the convergence speed. In fact, the SA method is suitable for large-scale optimization problems, especially for those in which a desired global minimum is hidden among many local minima. In a second step, real data in SE Iran are invertedto examine the usage and robustness of the proposed approach on real surface wave data. Then, we applied 3D gravity modeling based on surface wave analysis results to obtain the density structure of each layer. The reason for using both types of data sets is that the gravity anomaly does not have a good vertical resolution and surface wave group velocities are more appropriate for placing layer limits at depth, but they are not very sensitiveto density variations. Therefore, the use of gravity data increases the overall resolution of density distribution. Compared with the Shuffle Complex Evolution (SCE) method that was implemented in a previous study, we found out that the SA method is more stable and has less variability of model parameter values in successive tests. In the final step, we reapplied the SA method to invert the fundamental-mode Rayleigh wave group velocities based on the results of gravity modeling. Gravity results, such as thicknesses and densities were used to limit the searchspace in the SA method. Our results show that the Mohodepth across the Makran subduction zone is increasing from the Oman seafloor (24–30 km) and Makran forearc setting (34–42 km) to the Taftan-Bazman volcanic arc (47–49 km). Also, the results show high shear and compressional velocities under the Gulf of Oman, decreasing to the north of the Makran region. The density image shows an average crustal density with maximum values under the Gulf of Oman, decreasing northward to the Makran region

Tsunami hazard assessment in the Makran subduction zone

17 pages, 9 figures, 1 table. Other author's papers can be downloaded at http://www.denys-dutykh.com/International audienceThe lack of offshore seismic data caused uncertainties associated to understating the behavior of future tsunamigenic earthquakes in the Makran Subduction Zone (MSZ). Future tsunamigenic events in the MSZ may trigger significant near-field tsunamis. Run-up heights in the near-field are controlled by the heterogeneity of slip over the rupture area. Considering a non-planar geometry for the Makran subduction zone, a range of random k^{-2} slip models were generated to hypothesize rupturing on the fault zone. We model tsunamis numerically and assess probabilistic tsunami hazard in the near-field for all synthetic scenarios. The main affected areas by tsunami waves are the area between Jask and Ormara along the shorelines of Iran and Pakistan and the area between Muscat and Sur along the Oman coastline. The maximum peak-run-up along the shores of Iran and Pakistan is about 16 m and about 12 m for the Oman shoreline. The slip distributions control the run-up along the Makran coastlines. The dependency of run-up to the heterogeneity of slip is higher in the most impacted areas. Those areas are more vulnerable to tsunami hazard than other areas