Good Vibrations

Practitioners in the marine seismic industry have focused upon the benefits of enhanced low-frequency amplitudes in recent years: benefits to improved velocity model building with FWI (full waveform inversion), enhanced quantitative prediction of subsurface rock and fluid properties, and cleaner seismic event character for seismic interpretation. In some sense, the benefits of enhanced high-frequency amplitudes has less prominence, partly because the inescapable effects of absorption and dispersion are seen as insurmountable. I revisit this topic and show some encouraging solutions to enhance high-frequency signal content in seismic images. Temporal Frequency Loss: Attenuation Effects The introductory figure above is an unfortunate reminder that the resolution of seismic images is extremely coarse. At exploration targets in the range of 3 or 4 kilometers below the surface, the dominant seismic wavelength will be several tens of meters, so using a well-known rule-of-thumb that the visib

In a previous article on " Decision Making " I briefly acknowledged how catastrophic errors can arise in decisions, and the post-mortems of such failures provide quite powerful insights into the interplay of the many issues involved. In this article, I further consider how accidents can happen and how they can be avoided. In a nutshell, it requires a preoccupation with failure by the organization at all levels. I think this is compatible with the HSEQ ambitions of seismic service companies working in various energy industries. Systems With High Levels of Interactive Complexity A common theme in the case study analyses of catastrophic accidents is that they involved t ightly coupled systems . Tight coupling exists if different elements of an organizational system are highly interdependent and closely linked to one another, such that a change in one area quickly triggers changes in other aspects of the system.  Tightly coupled systems have four attributes: time-dependent proces

I confess that anisotropy is not a subject I ever had any passion for, but its relevance for seismic imaging is undisputed and increasing in profile. I attempt to untangle the complex nomenclature below and highlight implications of the various theory without including the mathematics. The relevance of different degrees of anisotropy are summarized for various global geological settings. Terminology Let us begin by defining the terms stress and strain . Stress is a physical quantity that expresses the force applied to some material exert on each other, while strain is the measure of the deformation of the material. The interplay between all the permutations of stress and strain affecting some material can be very complex. According to Hooke’s law for general anisotropic, linear elastic solid, there are eighty one (81) possible ways to relate stress and strain!  Note that elastic means the deformation is reversible. In reality, a seismic wave propagating through the earth loses some en

I compare some interesting aspects of Astronomy and Seismic Exploration. The most obvious differences related to the scale of observations, and the fact that astronomers rely upon 'passive' measurements and geophysicists typically create their own 'active' sources of energy. Both pursuits must overcome incredibly weak signal strengths, and both deploy a variety of sensors in creative ways to enhance the level of information in their data. Mapping the Heavens In this photo a camera in a fixed location takes a beautiful photo of the heavens on a clear night. In the background you can see a radio telescope dish pointing upwards. By precise mechanical control, such a dish can scan the sky, and accounting for the rotation of the earth, can also produce an image of the heavens – but over the range of frequencies and wavelengths corresponding to radio waves, rather than corresponding to visible light. As we will see, the resolution and insights gained by geophysicists deserve

I summarize and highlight elements of a large-scale multi-year experiments that quantified the impacts of exposure to a commercial seismic source on both an assemblage of tropical demersal fishes and pearl oysters targeted by commercial fisheries on the North West Shelf of Western Australia. Multiple lines of evidence suggest that seismic surveys have little impact on demersal fishes or pearl oysters in realistic environments.   The NWSSRP Study and the Marine Seismic Noise Measurement and Impact Theme In 2017, the Australian Institute of Marine Science (AIMS) and its partners commenced the North West Shoals to Shore Research Program (NWSSRP) , a three year, A$20 million study of the North West Shelf of Australia (refer to Figure 1). The program of 11 separate studies within four main themes has been conducted by a multidisciplinary team of scientists, technical staff and industry experts. Each of the four themes addressed gaps in scientific knowledge relevant to the environmental mana