Tomographic inversion for the seismic velocity structure beneath northern New England using seismic refraction data

1994 ◽  
Vol 99 (B8) ◽  
pp. 15331 ◽  
Author(s):  
Hong Zhu ◽  
John E. Ebel
Keyword(s):  
New England ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Tomographic Inversion ◽  
Seismic Velocity Structure ◽  
Northern New England ◽  
Seismic Refraction Data ◽  
Refraction Data

scholarly journals Detailed shallow structure seismic refraction investigation, with the application of different processing techniques

2001 ◽  
Vol 34 (4) ◽  
pp. 1309
Author(s):  
Τ. ΠΑΠΑΔΟΠΟΥΛΟΣ ◽  
Π. ΚΑΜΠΟΥΡΗΣ ◽  
Ι. ΑΛΕΞΟΠΟΥΛΟΣ
Keyword(s):  
Seismic Velocity ◽  
Seismic Refraction ◽  
Seismic Sources ◽  
Subsurface Structure ◽  
Seismic Refraction Data ◽  
Processing Techniques ◽  
National Road ◽  
Gradual Variation ◽  
Refraction Data ◽  
Shallow Structure

A comparative study of conventional and modern processing techniques of seismic refraction data is examined in this paper, for shallow structure investigation in the framework of a geotechnical research. The techniques used here were applied for the detection of narrow and low seismic velocity zones along the bedrock in the 10.5th Km of the new national road Igoumenitsa-Ioannina. The results were comparable and only slight deviations were observed due mainly to different algorithm procedures applied on data and the resolution provided by each technique. It is pointed out that the non linear tomography seismic refraction technique, overcomes the conventional ones since by increasing the number of seismic sources and considering the gradual variation of seismic velocity with depth, a better resolution and image reconstruction for the subsurface structure is obtained.

Hybrid shortest path and ray bending method for traveltime and raypath calculations

Geophysics ◽  
2001 ◽  
Vol 66 (2) ◽  
pp. 648-653 ◽  
Author(s):  
Harm J. A. Van Avendonk ◽  
Alistair J. Harding ◽  
John A. Orcutt ◽  
W. Steven Holbrook
Keyword(s):  
Ray Tracing ◽  
Shortest Path ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Computation Time ◽  
Hybrid Scheme ◽  
Seismic Velocity Structure ◽  
Order Of Magnitude ◽  
Ray Bending

The shortest path method (SPM) is a robust ray‐tracing technique that is particularly useful in 3-D tomographic studies because the method is well suited for a strongly heterogeneous seismic velocity structure. We test the accuracy of its traveltime calculations with a seismic velocity structure for which the nearly exact solution is easily found by conventional ray shooting. The errors in the 3-D SPM solution are strongly dependent on the choice of search directions in the “forward star,” and these errors appear to accumulate with traveled distance. We investigate whether these traveltime errors can be removed most efficiently by an SPM calculation on a finer grid or by additional ray bending. Testing the hybrid scheme on a realistic ray‐tracing example, we find that in an efficient mix ray bending and SPM account for roughly equal amounts of computation time. The hybrid method proves to be an order of magnitude more efficient than SPM without ray bending in our example. We advocate the hybrid ray‐tracing technique, which offers an efficient approach to find raypaths and traveltimes for large seismic refraction studies with high accuracy.

Coincident seismic-wave velocity and reflectivity properties of the lower crust beneath the Appalachian Front, west of Newfoundland

1991 ◽  
Vol 28 (1) ◽  
pp. 94-101 ◽  
Author(s):  
François Marillier ◽  
Mike Dentith ◽  
Karin Michel ◽  
Ian Reid ◽  
Brian Roberts ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Ultramafic Rocks ◽  
Seismic Reflection Profile ◽  
Crustal Extension ◽  
Seismic Wave Velocity ◽  
Seismic Velocity Structure ◽  
Iapetus Ocean ◽  
Deep Seismic Reflection Profile

We have determined the seismic velocity structure of the crust in the vicinity of the Appalachian deformation front off western Newfoundland and the adjacent Gulf of St Lawrence. These measurements were made from two perpendicular wide-angle seismic refraction profiles, one of which is collinear with a previously recorded deep seismic reflection profile. The Grenville foreland crust, about 45 km thick, is characterized by velocities of 6.35 km/s in its upper part and 6.7 km/s in its lower part. Close to the coast of Newfoundland, a deep crustal reflective wedge is bounded by a northwest-dipping reflector and by the crust–mantle boundary, which is at only 39 km depth beneath the wedge. In the wedge, velocities of 7.2–7.3 km/s may indicate the presence of mafic and ultramafic rocks. We speculate that several processes could have caused the high velocities and the high reflectivity. The most attractive is perhaps crustal extension with consequent underplating during the formation of the Iapetus Ocean or during later reactivation by Carboniferous strike-slip movements.

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