3d earthquake models for 6th graders how to

We used the Local Earthquake Tomography (LET) method to contribute to a better understanding of the crustal structure and its relationship to the upper mantle.ĭuring the last 15 years, several geophysical experiments significantly contributed to the present understanding of the relationship between the Pannonian and Dinaridic crusts. No high-resolution three-dimensional model of the Earth’s crust and uppermost mantle is available yet for the northern Dinarides and adjacent southwestern Pannonian basin, and this is the motivation for undertaking this research. This geophysical investigation addresses the contact area between the Adriatic microplate and European plate in the northern Dinarides, which belongs to a very complex tectonic system in the southern part of the European lithosphere. The strong velocity increase at depth of about 20 km indicates that the Dinaridic crust could be interpreted as two-layered, while the Pannonian crust is probably one-layered. A very pronounced high-velocity body is present in the transitional part between the Dinarides and the Pannonian basin at a depth range of 5–15 km. We find relatively high velocities below the northern Dinarides at shallow depths (< 10 km), and low velocities caused by deep local depressions in the Pannonian basin. The Moho surface was determined on the basis of the highest velocity gradients in the vertical cross-sections. Our study provides the first crustal three-dimensional seismic model of the studied area, and it is correlated with previous results in the survey area allowing us to infer the main crustal structures with high confidence. The velocity model reveals crustal thickening beneath the Dinarides and significant crustal thinning beneath the Pannonian basin.

Velocity variations are computed on a grid using the three-dimensional nonlinear tomographic inversion method. The data enabled to achieve a resolution of less than a hundred kilometres in horizontal directions and a few kilometres in vertical direction in the area with good ray coverage, as is documented by the resolution tests. Two data subsets were used in this study: (1) data recorded on 15 temporary seismic stations, which were deployed in Croatia in the framework of ALPASS-DIPS project, and (2) travel time datasets from the Croatian Seismological Survey and ORFEUS databases. Datasets of P-wave travel times are inverted to recover a three-dimensional P-wave velocity model of the survey area. We present the results of local earthquake tomography (LET) analysis to investigate the crust and uppermost mantle structure in the northern Dinarides and southwestern Pannonian basin.

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