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Crustal structure of the northern Dinarides and southwestern part of the Pannonian basin inferred from local earthquake tomography
Swiss Journal of Geosciences ( IF 3.1 ) Pub Date : 2019-01-04 , DOI: 10.1007/s00015-018-0335-2
Josipa Kapuralić , Franjo Šumanovac , Snježana Markušić

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. Datasets of P-wave travel times are inverted to recover a three-dimensional P-wave velocity model of the survey area. 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. 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. Velocity variations are computed on a grid using the three-dimensional nonlinear tomographic inversion method. 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. The Moho surface was determined on the basis of the highest velocity gradients in the vertical cross-sections. 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. 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. 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.

中文翻译:

根据局部地震层析成像推断北纳那利底群岛和潘诺尼盆地西南部的地壳结构

我们介绍了局部地震层析成像(LET)分析的结果,以调查北第纳里德和西南Pannonian盆地的地壳和最上层地幔结构。反转P波传播时间的数据集以恢复测量区域的三维P波速度模型。本研究使用了两个数据子集:(1)在ALPASS-DIPS项目框架内在克罗地亚部署的15个临时地震台站上记录的数据,以及(2)来自克罗地亚地震勘测和ORFEUS数据库的旅行时间数据集。分辨率测试表明,该数据能够在具有良好射线覆盖率的区域中实现水平方向上小于一百公里的分辨率以及垂直方向上几千米的分辨率。使用三维非线性层析成像反演方法在网格上计算速度变化。我们的研究提供了所研究区域的第一个地壳三维地震模型,并且与调查区域中的先前结果相关联,从而使我们能够高信度地推断主要地壳结构。速度模型揭示了Dinarides下面的地壳增厚,并且Pannonian盆地下面的地壳明显变薄。Moho表面是根据垂直截面中的最高速度梯度确定的。我们发现北纳那利底山脉以下较浅的深度(<10 km)具有相对较高的速度,而Pannonian盆地中的局部深陷引起的较低速度。Dinarides和Pannonian盆地之间的过渡部分存在一个非常明显的高速体,深度范围为5-15 km。深度约20 km处的强烈速度增加表明,狄拉尼纪地壳可以解释为两层,而Pannonian地壳可能是一层。
更新日期:2019-01-04
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