Dr James W. D. Hobro
Department of Earth Sciences, University of Cambridge .
From 1995 until 1999 I studied for a Ph.D. at the Bullard Laboratories as a member of Churchill College. I subsequently (1999-2000) held the post of Research Associate for the Cambridge Advanced Lithological Imaging Project (LITHOS), working on development and documentation of the seismic inversion code (Jive3D) developed during the course of my Ph.D. This page acts as my academic science home page and a point from which copies of my Ph.D. thesis and the Jive3D code may be downloaded. Since September 2000 I have been working for Schlumberger (and subsequently WesternGeco, formed by the merging of Schlumberger Geco-Prakla and Western Geophysical). I would like to thank the computing officers at Bullard for allowing me to maintain this page.
|Between 1995 and 1998 I developed a 3-D seismic tomographic inversion method called Jive3D. This is a seismic travel-time inversion package that is able to model complex sub-surface structures using combined reflection and refraction seismic data. Jive3D has been tested extensively on synthetic and real data sets and has been applied to data from a wide variety of survey types. The Jive3D code and documentation are currently available to download. See the Jive3D page for more details. Development of the Jive3D method formed the first part of my Ph.D. thesis, and was supervised by Dr Tim A. Minshull and Dr Satish C. Singh. The image shown here is a slice through a 3-D model produced by Jive3D and viewed in perspective.|
|I have applied the Jive3D inversion method to a 3-D wide-angle seismic data set that provides seismic velocity constraints on the methane hydrate stability zone in a region of the Cascadia Margin. The results revealed the 3-D variation in seismic P-wave velocity throughout the stability zone. This study formed the second part of my Ph.D. thesis and was also supervised by Dr Tim A. Minshull and Dr Satish C. Singh. A map of this region of the Cascadia Margin is shown, centred on the location of the survey used in this analysis.|
|Although fission track analysis is widely used as a means of dating minerals, there are many uncertainties inherent in the methods currently used to estimate track volume density and uranium concentration. The density of track intersections with a prepared mineral surface is normally measured by etching the mineral and illuminating the surface with reflected light. In the External Detector method, however, more information on the track density in the detector may be obtained by examining the image in more detail, and in particular, by measuring the distribution of track intersection areas. This work is done in collaboration with Dr John A. Miller. The image shown here is the surface of an external mica detector under reflected light, showing many track intersections and interference fringes from a few oblique tracks.|