scholarly journals Surface and near-surface geology, Navarin Basin province; results of the 1980-81 field seasons

1984 ◽  
Author(s):  
Herman A. Karl ◽  
P.R. Carlson
Keyword(s):  
Near Surface ◽  
Surface Geology

scholarly journals Towards a national 3D geological model of Denmark

2016 ◽  
Vol 35 ◽  
pp. 27-30
Author(s):  
Peter B.E. Sandersen ◽  
Thomas Vangkilde-Pedersen ◽  
Flemming Jørgensen ◽  
Richard Thomsen ◽  
Jørgen Tulstrup ◽  
...  
Keyword(s):  
Subsurface Layer ◽  
Geological Model ◽  
Technical Standards ◽  
Near Surface ◽  
Subsurface Geology ◽  
3D Geological Model ◽  
Combining Data ◽  
National Model ◽  
Surface Geology ◽  
2D To 3D

As part of its strategy, the Geological Survey of Denmark and Greenland (GEUS) is to develop a national, digital 3D geological model of Denmark that can act as a publicly accessible database representing the current, overall interpretation of the subsurface geology. A national model should be under constant development, focusing on meeting the current demands from society. The constant improvements in computer capacity and software capabilities have led to a growing demand for advanced geological models and 3D maps that meet the current technical standards (Berg et al. 2011). As a consequence, the users expect solutions to still more complicated and sophisticated problems related to the subsurface. GEUS has a long tradition of making 2D maps of subsurface layer boundaries and near-surface geology (Fredericia & Gravesen 2014), but in the change from 2D to 3D and when combining data in new ways, new geological knowledge is gained and new challenges of both technical and organisational character will arise. The purpose of this paper is to present the strategy for the national 3D geological model of Denmark and the planned activities for the years ahead. The paper will also reflect on some of the challenges related to making and maintaining a nationwide 3D model. Initially, the model will only include the Danish onshore areas, with the Danish offshore areas and Greenland to be added later using a similar general setup.

Directional site resonances and the influence of near-surface geology on ground motion

1991 ◽  
Vol 18 (5) ◽  
pp. 901-904 ◽  
Author(s):  
Ornella Bonamassa ◽  
John E. Vidale ◽  
Heidi Houston ◽  
Susan Y. Schwartz
Keyword(s):  
Ground Motion ◽  
Near Surface ◽  
Surface Geology

scholarly journals Characterization of a complex near-surface structure using well logging and passive seismic measurements

2016 ◽  
Author(s):  
Beatriz Benjumea ◽  
Albert Macau ◽  
Anna Gabàs ◽  
Sara Figueras
Keyword(s):  
Wave Velocity ◽  
Upper Cretaceous ◽  
Seismic Velocity ◽  
Well Logging ◽  
P Wave ◽  
Geophysical Field ◽  
Near Surface ◽  
Passive Seismic ◽  
Surface Geology ◽  
Seismic Measurements

Abstract. We combine geophysical well logging and passive seismic measurements to characterize the near surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, decreasing seismic velocity with depth is expected. The geophysical datasets used in this study include sonic and gamma ray logs at two boreholes and passive seismic measurements: 224 H/V stations and 3 arrays. Well logging data defines two significant changes in the P-wave velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps for its interpretation. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

RELATION OF SEISMIC CORRECTIONS TO SURFACE GEOLOGY

Geophysics ◽  
1952 ◽  
Vol 17 (2) ◽  
pp. 218-228 ◽  
Author(s):  
H. M. Thralls ◽  
R. W. Mossman
Keyword(s):  
Seismic Data ◽  
Reference Plane ◽  
Illinois Basin ◽  
Low Velocity ◽  
Near Surface ◽  
Low Velocity Layer ◽  
Surface Geology ◽  
Velocity Layer ◽  
Layer Problem

The arbitrary application of any set type of near‐surface corrections to seismic data can lead to erroneous results. The determination of the type of correction to be used must be based, in part, on the type of formations present in the near‐surface. Case studies are offered to illustrate conditions arising in areas of youthful and mature topography. Specifically, they deal with a complex low velocity layer problem in a river valley, a pre‐glacial topography in the Illinois Basin, a problem arising in a mature topography in Kansas, and a youthful topography in central Wyoming. In such cases, the use of a “floating” elevation reference plane is advocated for the “Correction Zone” lying immediately below the surface.

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