Emily A. Hinz

Ground-Penetrating-Radar Reflection Attenuation Tomography with an Adaptive Mesh

Ground-penetrating radar GPR attenuation-difference analysiscanbeausefultoolforstudyingfluidtransportinthe subsurface. Surface-based reflection attenuation-difference tomography poses a number of challenges that are not faced by crosshole attenuation surveys. We create and analyze a synthetic attenuation-difference GPR data set to determine methods for processing amplitude changes and inverting for conductivity differences from reflection data sets. Instead of usingatraditionalgrid-basedinversion,weuseadata-driven adaptive-meshing algorithm to alter the model space and to createamoreevendistributionofresolution.Adaptivemeshing provides a method for improving the resolution of the modelspacewhilehonoringthedatalimitationsandimproving the quality of the attenuation difference inversion. Comparinginversionsonaconventionalrectangulargridwiththe adaptive mesh, we find that the adaptively meshed model reduces the inversion computation time by an average of 75% with an improvement in the root mean square error of up to 15%. While the sign of the conductivity change is correctly reproduced by the inversion algorithm, the magnitude varies byasmuchasmuchas50%fromthetruevalues.Ourheterogeneous conductivity model indicates that the attenuation differenceinversionalgorithmeffectivelylocatesconductivity changes, and that surface-based reflection surveys can producemodelsasaccurateastraditionalcrossholesurveys.

Seismic refraction at ancestral Puebloan sites on the Pajarito Plateau, New Mexico

Abstract Geophysical techniques can be used for non-invasive surveys at archaeological sites. One under-utilized technique, seismic refraction, has many potential applications. It is an inexpensive, efficient way to characterize subsurface deposits, especially at sites with shallow accumulations over bedrock. Archaeologists and geophysicists participating in the Summer of Applied Geophysics Experience from Los Alamos National Laboratory and Bandelier National Monument on the Pajarito Plateau in northern New Mexico characterized Ancestral Puebloan sites (A.D. 1200–1450) using this technique. We provide an overview of how seismic refraction works and demonstrate the applicability of seismic refraction for identifying buried archaeological features such as communal structures and walls.

Student-based archaeological geophysics in northern Thailand

Summary As part of the 2010 near-surface geophysics workshop in Chiang Mai, Thailand, local archaeological targets were used as a basis for teaching geophysical data collection, processing, and interpretation techniques. By addressing local issues and interests, the workshop was able to demonstrate to participants and the local community how near-surface geophysics can be applied using simple survey methods and low-cost processing techniques.

The establishment of a geophysics field camp in northern Thailand

As a participant in SEGs Geoscientists Without Borders program, we have developed a geophysics field camp in northern Thailand to train students and professionals from throughout Southeast Asia in field-based geophysical methods. Over the past two years, faculty, technicians, professionals, and students from 18 institutions and 11 countries have acquired, processed, and interpreted geophysical data at field sites in and around Chiang Mai, Thailand. Participation from undergraduate students, graduate students, and private and public sector geoscience professionals provides a broad base of experience, background, and insight. Our training has provided opportunities for cross-cultural collaboration and education, and a greater use of field-based geophysical methods for academic, private sector, and government agencies throughout Southeast Asia.

Southeast Asia applied geophysics workshop: Geoscientists without borders

Summary As first-round recipients of the SEG Foundation Geoscientists Without Borders program, we conducted a geophysics workshop in northern Thailand to train students and professionals in geophysical methods to address environmental and engineering challenges. Faculty, technicians, professionals and students from fifteen participating institutions from seven countries acquired, processed and interpreted geophysical data at four separate sites in Chiang Mai, Thailand. These field sites were selected to train participants in the use of a variety of geophysical methods to address groundwater, archaeology, and geohazard concerns. The workshop consisted of one week of data acquisition followed by a week of data analysis for seismic, ground penetrating radar, electrical, electromagnetic, gravity, and magnetic data. Participants learned geophysical theory while acquiring, processing, and interpreting geophysical datasets. At the end of the workshop, participants documented and presented their results. Final products from the GWB-sponsored field training including a 125-page student generated field camp report and a 180-slide presentation. Photos and technical information can be found and downloaded at http://cgiss.boisestate.edu/gwb