ALBERT

Beschreibung: The Aboriginal population of the Aṉangu Pitjantjatjara Yankunytjatjara (APY) lands in South Australia is dependent on groundwater for nearly all water needs. In that region, placement of wells in productive aquifers of appropriate water quality is challenging because of lack of hydrologic data and variable aquifer properties. It is desirable to have an improved ability to identify and evaluate groundwater resources in this remote region with cost-effective methods that make minimal impact on the environment. A project supported by the Society of Exploration Geophysicists program Geoscientists Without Borders tested a combined geophysical approach with airborne and ground-based data sets to locate a potential aquifer, confirm water content, and estimate the subsurface extent of the water-bearing zone. This hydrogeophysical approach was an effective means for exploration and evaluation of groundwater resources in APY lands generally, and it characterized a specific aquifer as a case study.

Beschreibung: Ground-penetrating radar (GPR) was used to map the warrens of southern hairy-nosed wombats ( Lasiorhinus latifrons ) in South Australia in a variety of soil types. Although farmers often cull wombats to reduce their impact on infrastructure and agriculture, their population dynamics are poorly understood, and all stakeholders agree that better information is required. Warrens were mapped successfully at four locations, providing insight into how soil type and local conditions affect burrow morphology and how these can influence population abundance. The use of GPR has provided the first noninvasive means of mapping wombat warrens and the first opportunity to conduct follow-up research to determine how warrens might change over time in response to changes in population.

Beschreibung: Haiti is one of the most impoverished nations in the world and is highly susceptible to earthquakes. An important part of seismic design is the measurement of the dynamic properties of soil and calculation of site-specific seismic site response. However, there is a capability gap in that geoscientists in Haiti might not be trained to carry out a proper analysis. A humanitarian project sponsored by the Society of Exploration Geophysicists Foundation program Geoscientists Without Borders was conducted to address that deficiency. The scope of the project included field geophysical seismic surface-wave testing at selected sites in Haiti, calculation of shear-wave velocity profiles, and calculation of seismic site response. A user's manual was written and given to a humanitarian engineering group active in Haiti along with the equipment used to perform field testing at the conclusion of the project. Efforts such as this enhance the self-sufficiency of Haiti with respect to seismic design, which ultimately will result in reduced loss of life during future earthquakes.

Beschreibung: For the third installment in our interview series, Ray Scippa, director of internal communications at ConocoPhillips, sat down with Hervé Coutrix, president and CEO of Total E&P Research and Technology USA.

Beschreibung: The coastal city of Cotonou in the developing country of Bénin, West Africa, is a large population center that is facing a serious threat to the sustainability of its freshwater supply. The city relies on the Godomey aquifer for domestic water, but the aquifer is undergoing saltwater intrusion. This problem is likely to worsen without significant steps to improve management of the water supply. Aquifer continuity and saltwater flow paths are poorly understood, but that information is critical to ensure sustainable access to freshwater in this growing urban center. In January 2012, a two-year geophysical investigation was begun with the prime objective of using the seismic-reflection method to better understand the continuity of the primary aquifer units. That information then can be used to inform and improve the regional groundwater flow model. The project presented many challenges, both technical and cultural, including the language barrier, conducting fieldwork in the developing world with a limited budget, and the complicated logistics of acquiring seismic data in a congested urban environment. Despite these challenges, the seismic investigation was completed successfully, and results show that the aquifer system is substantially more complicated than previously thought. Critically, at least one paleochannel cuts through a substantial portion of the aquifer system and truncates multiple aquifer/aquitard boundaries. These boundary truncations appear to provide connected pathways among aquifers that previously were thought to be isolated and might explain recent hydrologic observations. Although the full impact of these findings is yet to be determined, it is clear that the seismic study has provided valuable information that improves the understanding of the system and ultimately will aid in management of the groundwater resource in Cotonou.

Beschreibung: On 12 January 2010, Haiti suffered a magnitude 7.0 earthquake near Port-au-Prince, which resulted in a catastrophic loss of life and infrastructure. The effects were particularly severe on the Léogâne fan delta, close to the earthquake's epicenter. Because no unambiguous rupture to the surface has been found, the suspected fault that caused the event has been labeled "blind." A geophysical team from the University of Houston has undertaken expeditions to Haiti in 2012–2014, with support from the SEG Geoscientists Without Borders program, to try to help build Haiti's geophysical capability and assist in finding subsurface evidence of the proposed blind fault. The team reconnoitered the epicentral region of the 2010 earthquake and selected sites on the Léogâne delta fan for land surveys. The team enjoyed a productive and pleasant interaction with local villagers while receiving access to survey areas and assistance with operations. The resulting 2012 seismic and gravity data provided promise for more detailed surveys that the team undertook in February 2013. Measurements indicated that the soil sediments near Léogâne are Class E — a substantial geohazard. The University of Houston team found a broad and unfaulted anticline in the overlying fan deposit that is consistent with seismogenic movement on a north-dipping reverse fault at greater depth. The axis of the subsurface anticline is in alignment with an east-west-trending zone of localized highway damage and a coral reef that was uplifted during the 2010 earthquake. Lake sonar surveys have given some excellent images of the associated Enriquillo–Plantain Garden fault zone (EPGFZ). As a result of this work, the team plans to bring larger seismic sources to create more detailed and deeper seismic sections (land and lake) and to assist in further development of Haitian geophysical capabilities. The project has provided a remarkable learning experience for staff and students as well as for Haitian colleagues.

Beschreibung: In this tutorial, we will explore two topics that are particularly relevant to quantitative seismic interpretation — thin-bed tuning and AVO analysis. Specifically, we will examine the impact of thin beds on prestack seismic amplitudes and subsequent effects on AVO attribute values.

Beschreibung: Statistical white reflectivity, minimum-phase wavelets, and stationarity are regarded to be three major shortcomings in dealing with the Robinson convolution model. Modern reflectivity inversion methods (e.g., constrained reflectivity inversion) mainly attempt to reduce side effects of the first two assumptions, but most of them overlook the important fact that seismic signals are typically nonstationary. Numerical tests and practical applications have verified that nonstationarity does have great influence on reflectivity estimation and probably would result in misplaced positions or wrongly restored amplitudes for estimated reflectivity. Nonstationarity can be tackled from a perspective of hyperbolic smoothing in Gabor deconvolution. Specially, the energy relationship of hyperbolic strips in a log spectrum can be taken as a quantitative indicator in balancing nonstationarity and conditioning seismic traces to the assumption of unchanging wavelets. Applications to marine seismic data show that balancing nonstationarity finally helps to recover subtle reflectivity information and promotes better displays of geologic features of the subsurface.

Beschreibung: This special section of The Leading Edge and the broad engagement from the SEG community show that geophysics can make a considerable difference to communities in need. This month's special section on humanitarian geophysics brings together a wide array of geophysical studies to address a diverse set of topics with a common theme of improving the lives of disadvantaged populations. These studies and included articles cover three continents and move beyond hazards and resource evaluations that are typical of geophysical case studies to educate, inform, and engage local communities.

Beschreibung: The American Geophysical Union's Thriving Earth Exchange advances humanitarian geophysics by helping scientists, communities, and sponsors connect and launch projects that use earth and space science to help address practical priorities, one community at a time. Scientists are any learning, practicing, or retired professional from industry or academia; communities are geographic, cultural, ethnic, or professional groups coalesced around shared priorities; and sponsors are funders or advocates who would like to enable and learn from projects. Using crowd-sourcing and social-networking tools, the Thriving Earth Exchange will catalyze community science so that community leaders, scientists, and sponsors work as partners to generate and apply scientific insight. The exchange will help project leaders to explore ideas, form partnerships, design projects, and connect with the human, technological, and capital resources they need to carry out those projects. Because the exchange supports and links a diverse set of interactions, project leaders can go all the way from exploring broad connections between science and community priorities to launching specific, actionable, science-based projects. All this occurs in an open environment that invites broad participation, facilitates reuse of innovative solutions, and builds trust between scientists and nonscientists.