Application of stacking and inversion techniques to three-dimensional wide-angle reflection and refraction seismic data of the Eastern Alps

Abstract

SUMMARY We present new methods for the interpretation of 3‐D seismic wide‐angle reflection and refraction data with application to data acquired during the experiments CELEBRATION, 2000 and ALP 2002 in the area of the Eastern Alps and their transition to the surrounding tectonic provinces (Bohemian Massif, Carpathians, Pannonian domain, Dinarides). Data was acquired on a net of arbitrarily oriented seismic lines by simultaneous recording on all lines of seismic waves from the shots, which allows 2‐D and 3‐D interpretations. Much (80%) of the data set consists of crossline traces. Low signal to noise (S/N) ratio in the area of the young orogens decreases the quality of travel time picks. In these seismically heterogeneous areas it is difficult to assign clearly defined arrivals to the seismic phases, in particular on crossline record sections. In order to enhance the S/N ratio, signal detection and stacking techniques have been applied to enhance the Pg‐, Pn‐ and PmP phases. Further, inversion methods have been developed for the interpretation of WAR/R‐data, based on automated 1‐D inversion (Pg) and the application of the delay time concept (Pn). The results include a 3‐D velocity model of the crust based on Pg waves, time and depth maps of the Moho and a Pn‐velocity map. The models based on stacked data are robust and provide a larger coverage, than models based on travel time picks from single‐fold (unstacked) traces, but have relatively low resolution, especially near the surface. They were used as the basis for constructing models with improved resolution by the inversion of picks from single‐fold data. The results correlate well with geological structures and show new prominent features in the Eastern Alps area and their surrounds. The velocity distribution in the crust has strong lateral variations and the Moho in the investigation area appears to be fragmented into three parts.

Sn propagation in the Western United States from common midpoint stacks of USArray data

“…Stacking methods can greatly enhance such weak arrivals [e.g., Richards-Dinger and Shearer, 1997]. Common midpoint stacks are typically applied in seismic reflection experiments, but a similar approach can be used with refracted arrivals to obtain information on average seismic properties within a certain region [Behm et al, 2007]. Here we stack seismograms that have the midpoint of their ray paths within a common two-dimensional cell.…”

“…[9] We proceed in similar fashion to that described in Behm et al [2007]: We shift an equal area square cell with a width of 1.6 ı in increments of 0.8 ı across the Western United States. At each location, we find the event and station combinations that have their range midpoint within the window.…”

Lithospheric Structure and Tectonics of the Eastern Alps – Evidence from New Seismic Data

“…Destructive plate boundaries can be identified by offsets of an otherwise smooth Moho boundary derived from controlled source seismic data (Waldhauser et al, 1998;Abramovitz and Thybo, 2000;Kissling et al, 2006;Brückl et al, 2007); natural source seismic methods like receiver functions and tomographic inversion also have the potential to clearly resolve destructive Moho boundaries (e.g., Kummerow et al, 2004;Di Stefano et al, 2009). Continental transform or transfer faults may exist without significant offsets of the Moho boundary (Weber et al, 2009;Thybo et al, 2003;Zhao et al, 2001 (Behm et al, 2007). These data on Moho depth were also integrated into the European Moho-map of Grad et al (2008).…”

“…The Moho fragmentation between Adria and Liguria was extended to south east using tomographic data from Di Stefano et al (2009). In the Eastern Alps, seismic profiles and the Moho-map indicate a fragmentation of the lithosphere into three blocks, the European plate, the Adriatic microplate, and a newly interpreted Pannonian fragment (Brückl et al, 2007;Behm et al, 2007). Brückl et al (2010) applied 2D elastic plate modelling of the lithosphere to decide if a continuous plate is an appropriate model or if the introduction of a plate boundary yields a better fit.…”

“…These data on Moho depth were also integrated into the European Moho-map of Grad et al (2008). For further considerations, the Moho-map by Grad et al (2009) is used together with the original data of Behm et al (2007). Depth and offset of the Moho at the plate boundaries determined by Waldhauser et al (1998) were integrated.…”