- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 1, Issue 9, 1983
First Break - Volume 1, Issue 9, 1983
Volume 1, Issue 9, 1983
-
-
Deep Seismic Reflection Profiling Onshore United Kingdom
Authors A. Whitaker and A. ChadwickOver the last few years the Deep Geology Unit of the Institute of Geological Sciences (IGS), with the support of the Natural Environment Research Council's (NERC) Deep Geology Committee, has been acquiring and interpreting seismic reflection data of six seconds, or greater, two-way travel time (TWTI). The purpose of the work is to study the continental crust beneath the UK landmass particularly at levels deeper than those examined on a routine basis by exploration companies. This account discusses some details of individual surveys and presents notes on field parameters, data quality and factors affecting data quality, and interpretation. In general, interpretation work, supplemented by data from relatively shallow reflection surveys and borehole information is showing a consistency of seismic structure of the Earth's crust beneath Britain despite the relatively scattered nature of the data points. The seismic lines themselves, ranging in length from 1.5 to 30 km, have been shot in various, widely separated parts of the country. Not all of the data available to the Unit is discussed in this paper for reasons of confidentiality, but all data has been taken into account in discussion of recommendations for deep data acquisition. Three principal approaches have been used to acquire data: (1) Lines commissioned by IGS, some on behalf of NERC, and shot by a commercial seismic prospecting company. (2) Lines shot by IGS using in-house equipment but processed commercially. (3) Lines shot as commercial hydrocarbons surveys but with record length increased using funds provided by IGS and NERC. The first approach is the most effective in that choice of location and energy source are determined by Deep Geology Unit; speed of data acquisition is a great advantage but the method is expensive (the cost is variable depending on the energy souree used). The second approach is less expensive and allows choice of location, but an explosive energy source is necessary at present; this involves drilling shotholes and therefore a relatively slow rate of data acquisition. The third approach is relatively inexpensive because the cost is limited virtually to the extra processing required. Disadvantages are that there is no control by Deep Geology Unit over acquisition techniques and location. The individual surveys are not illustrated by seismic sections. However, the Deep Geology Unit will inform enquirers which surveys are on open file.
-
-
-
Reflected Refracted Events
Authors G.A. Day and J.W.F. EdwardsRefracted rays do not normally produce events on seismic sections. Muting before stacking is designed to remove any far-trace arrivals due to refracted rays travelling along a high velocity layer, but if these same rays are reflected at a discontinuity in the high velocity interface they can produce events in the record. Here we will consider as reflected refractors those rays which retrace their path in the refracting medium, returning to the surface along a path parallel and near to their outgoing path.
-
-
-
Computer Science for Geophysicists. Part II: Seismic Computer System Architecture
By L. HattonAfter introducing some of the jargon in Part I of this series, I thought that I would continue the hardware side of things in the first half of this article by going on to describe the actual architecture of a seismic computer system in a little more detail. Whilst I am doing this, the topics of computer buses, channels and I/O bandwidth will be introduced as will their relationship with the potential bottlenecks in such a computer system. Although software will be touched on, it will not be considered in depth until later on in this series. In the second half, I will trace a line of high-level language right down through a hypothetical machine to its actual execution in the CPU.
-
Volumes & issues
-
Volume 42 (2024)
-
Volume 41 (2023)
-
Volume 40 (2022)
-
Volume 39 (2021)
-
Volume 38 (2020)
-
Volume 37 (2019)
-
Volume 36 (2018)
-
Volume 35 (2017)
-
Volume 34 (2016)
-
Volume 33 (2015)
-
Volume 32 (2014)
-
Volume 31 (2013)
-
Volume 30 (2012)
-
Volume 29 (2011)
-
Volume 28 (2010)
-
Volume 27 (2009)
-
Volume 26 (2008)
-
Volume 25 (2007)
-
Volume 24 (2006)
-
Volume 23 (2005)
-
Volume 22 (2004)
-
Volume 21 (2003)
-
Volume 20 (2002)
-
Volume 19 (2001)
-
Volume 18 (2000)
-
Volume 17 (1999)
-
Volume 16 (1998)
-
Volume 15 (1997)
-
Volume 14 (1996)
-
Volume 13 (1995)
-
Volume 12 (1994)
-
Volume 11 (1993)
-
Volume 10 (1992)
-
Volume 9 (1991)
-
Volume 8 (1990)
-
Volume 7 (1989)
-
Volume 6 (1988)
-
Volume 5 (1987)
-
Volume 4 (1986)
-
Volume 3 (1985)
-
Volume 2 (1984)
-
Volume 1 (1983)