Reply to Interactive comment of Franjo Šumanovac (Referee) on “Estimation of near-surface attenuation in the tectonically complex contact area of the Northwestern External Dinarides and the Adriatic foreland” by S. Markušić et al (original) (raw)
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Natural Hazards and Earth System Sciences Discussions, 2019
Seismic-induced ground motion at a site is generally influenced by seismic source, propagation path and local site conditions. Over the last several decades, researchers have consistently asserted that for near site attenuation, the spectral parameter kappa is subject primarily to site conditions. In this research we estimated parameter kappa based on the acceleration amplitude spectrum of shear waves, from the selected recordings of local earthquakes from seismological stations situated in the western part of Croatia from the slope of the high-frequency part. The spatial distribution of individual kappa values is compared with the azimuthal distribution of earthquake epicentres, with 30 values and the published coda-Q values for each station, as well as with isoseismal maps for several stronger events in the investigated area, along with the geological features. The dextral shift of crustal segments and frontal thrust of the External Dinarides along the Kvarner fault zone has probably had an impact on the geometry of the kappa parameter contour lines. These results are important for gaining further insight into the attenuation of near-surface crust layers in the Northwestern External Dinarides and the associated Adriatic foreland, as well as in similar geotectonic settings.
Geophysical Journal International, 2011
Broad-band seismograms of teleseismic events recorded at the Croatian Seismological Network were used to compute radial receiver functions (RFs) for eight locations in the External Dinarides. Waveform modelling was performed by a multistep matching of the theoretical RFs computed for horizontally layered 1-D isotropic models with the averaged observed RFs. Constraints from existing deep seismic sounding profiles, traveltime curves of regional crustal seismic phases and intuitive inferences gained from interactive forward modelling were used to construct initial 1-D models of the Earth. A non-linear inversion was performed in two stepsa grid search followed by the Monte Carlo search for the model parameters. Concurrently, RFs from different azimuths were stacked to obtain trade-off estimates of crustal thickness versus V p /V s ratios. The Moho depths were found in the range from around 40 km for Northern Adriatic stations to over 55 km for stations in the central part of the External Dinarides. Comparing our results with recent maps of the Moho topography inferred from seismic and gravimetric data, we find that for some stations the agreement between our results and the existing Moho maps is very good. For the others, we find the Mohorovičić discontinuity to be considerably deeper, indicating some of the thickest crust in Europe. Although it is plausible that such a deep Moho could be a consequence of a complex tectonic setting of the region (e.g. overlapping of two large tectonic units-the Adriatic microplate and the Dinarides), this result will have to be verified in the future studies using various other geophysical techniques.
Geophysical Journal International, 2009
The area of this study includes the contact between the Dinarides and the Pannonian basin, as a relation between the Adriatic microplate and Pannonian segment. Our analysis was carried out on profile Alp07, which is a part of the ALP 2002 experiment. ALP 2002 was large international seismic experiment that focused on the lithospheric structure of the Eastern Alps and surrounding areas. Profile Alp07 is one of several refraction and wide-angle reflection profiles located in the transition from the Adriatic microplate, through the Dinarides, and into the Pannonian basin. This 300-km-long profile extends from Istra, Croatia to the Drava River at Hungarian-Croatian border in a WSW-ENE direction. It is oriented approximately perpendicular to the Dinarides, the main faults in the Adriatic region, and the contact between the Dinarides and Pannonian basin. 2-D seismic modelling was done using tomographic inversion and ray tracing techniques. The Moho depth is the greatest in the area of the Dinarides, reaching about 40 km and is shallowest (30-20 km) in the Pannonian basin area. At the boundary between these provinces, the depth changes rather suddenly. In order to obtain additional constraints on the crustal structure, 2-D gravity modelling was also performed. The layer boundaries were retained from the seismic model as there was no need to change them during modelling, since varying densities in the model produced a good fit to the data. A geological model was constructed based on both geophysical models. Three types of the crust were found along profile: the Dinaridic and the Pannonian crusts that are separated by a relatively narrow transition zone. The Dinaridic upper crust is characterized by low seismic velocities and densities, but its lower crust has high velocities and densities. The Pannonian crust can be seen as unique layer characterized by both low seismic velocities and densities. Large lateral and vertical changes in densities and seismic velocities can be found in the transition zone. Troughs in the seismic model at the level of the Mohorovičić discontinuity are interpreted as major faults in the lithosphere. Three main lithospheric faults were identified: in northeastern part of the Dinarides under the Sava depression and under the Drava depression. The first one may be considered as a result of subduction of the Adriatic microplate under the Pannonian segment. Similar movements are also defined within the transition zone, where the Pannonian segment is gradually rising over on the Adriatic microplate.
Attenuation tomography of the Southern Apennines (Italy)
Journal of Seismology, 2008
The aim of this study is to improve our knowledge of the attenuation structure in the Southern Apennines using a new amplitude ratio tomography method (Phillips et al., Geophys Res Lett 32(21): L21301, 2005) applied on both direct and coda envelope measurements derived from 150 events recorded by 47 stations of the Istituto Nazionale di Geofisica e Vulcanologia National Seismic Network (Rete Sismica Nazionale Centralizzata). The twodimensional (2-D) analysis allows us to take into account lateral crustal variations and heterogeneities of this region. Using the same event and station distribution, we also applied a simple 1-D methodology, and the performance of the 1-D and 2-D path assumptions is tested by comparing the average interstation variance for the path-corrected amplitudes using coda and direct waves. In general, coda measurement results are more stable than using direct waves when the same methodology is applied. Using the 2-D approach, we observe more stable results for both waves. However, the improvement is quite small, probably because the crustal heterogeneity is weak. This means that, for this region, the 1-D path assumption is a good approximation of the attenuation characteristics of the region. A comparison between Q tomography images obtained using direct and coda amplitudes shows similar results, consistent with the geology of the region. In fact, we observe low Q along the Apennine chain toward the Tyrrhenian Sea and higher values to the east, in correspondence with the Gargano zone that is related to the Apulia Carbonate Platform. Finally, we compared our results with the coda Q values proposed by Bianco et al. (Geophys J Int 150:10-22, 2002) for the same region. The good agreement validates our results as the authors used a completely independent methodology.
07-Tectonophysics1993-Hatzidimitriou_et_al.pdf
Hatzidimitriou, P., Papazachos, C., Kiratzi, A. and Theodulidis, N., 1993. Estimation of attenuation structure and local earthquake magnitude based on acceleration records in Greece. In: S.J. Duda and T.B. Yanoskaya (Editors), Estimation of Earthquake Size. Tectonophysics, 217 (spec. sect.): 243-253.