Abstract
Abstract. The advent of cable-free nodal arrays for conventional seismic reflection and refraction experiments is changing the acquisition style for active-source surveys. Instead of triggering short recording windows for each shot, the nodes are continuously recording over the entire acquisition period from the first to the last shot. The main benefit is a significant increase in geometrical and logistical flexibility. As a by-product, a significant amount of continuous data might also be collected. These data can be analyzed with passive seismic methods and therefore offer the possibility to complement subsurface characterization at marginal additional cost. We present data and results from a 2.4 km long active-source profile, which have recently been acquired in western Colorado (US) to characterize the structure and sedimentary infill of an over-deepened alpine valley. We show how the “leftover” passive data from the active-source acquisition can be processed towards a shear wave velocity model with seismic interferometry. The shear wave velocity model supports the structural interpretation of the active P-wave data, and the P-to-S-wave velocity ratio provides new insights into the nature and hydrological properties of the sedimentary infill. We discuss the benefits and limitations of our workflow and conclude with recommendations for the acquisition and processing of similar datasets.
Highlights
Seismic nodal acquisition systems (“nodes” hereafter) were introduced to the active-source exploration community within the last decade with the promise of geometrical flexibility and more efficient production, especially in rugged terrain (Freed, 2008; Dean et al, 2013)
Processing passive data provides complementary information when compared to active data, e.g., surface wave inversion obtained from interferometry results in shear wave velocity models, and travel time tomography using local or regional seismicity can increase the investigation depth
We apply seismic interferometry to the continuous data to extract dispersive surface waves, which in turn are inverted for a 2-D shear wave velocity model of the valley structure
Summary
Seismic nodal acquisition systems (“nodes” hereafter) were introduced to the active-source exploration community within the last decade with the promise of geometrical flexibility and more efficient production, especially in rugged terrain (Freed, 2008; Dean et al, 2013). Processing passive data provides complementary information when compared to active data, e.g., surface wave inversion obtained from interferometry results in shear wave velocity models, and travel time tomography using local or regional seismicity can increase the investigation depth. We apply seismic interferometry to the continuous data to extract dispersive surface waves, which in turn are inverted for a 2-D shear wave velocity model of the valley structure. This model complements the results from activesource processing, and the joint interpretation of the active P-wave velocity and passive S-wave velocity models allows for new insights on the nature and hydrologic properties of the sedimentary valley infill
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