Mark Hudson is a Research Geologist with the Geosciences and Environmental Change Science Center
Science and Products
Ozark Dome-Arkoma Basin-Ouachita Transect
The Ozark Dome-Arkoma Basin-Ouachita Transect (ODABOuT) project examines the three-dimensional geology of a transect of the southern orogenic margin of North America in its best surface exposure in western Arkansas. The Ozark Dome and Arkoma Basin represent a foreland uplift and foreland basin that formed as a result of the impinging Ouachita orogenic belt. Understanding the geometry and evolution...
Geologic Mapping Studies at Buffalo National River, Northern Arkansas
Detailed geologic mapping is being conducted by the USGS in and adjacent to the Buffalo National River, a park administered by the National Park Service, to better understand and characterize the natural resources and associated ecosystems of this area within the Ozark Plateau region. General-purpose geologic maps are created to provide a framework for a host of natural resource, natural history...
Literature compilation of paleocurrent data from the Late Paleozoic Ouachita orogen, Oklahoma-Arkansas, U.S.A.
This digital geospatial compilation gathered paleoflow indicators from current-formed sedimentary structures throughout the Paleozoic Ozark uplift, Arkoma foreland basin, and Ouachita fold-thrust-belt of eastern Oklahoma and western Arkansas from existing publications. This dataset consists of unidirectional and bidirectional paleocurrents observed from a variety of bedform types represented by ap
Fault data collected between 1996 and 2019 from the Buffalo River watershed area, northern Arkansas
Information on the locations and characteristics of faults were collected while conducting fieldwork between 1996 and 2019 in support of geologic mapping in the Buffalo River watershed area of northern Arkansas. A total of 1274 entries on faults were recorded at 452 sites. The observations associated with faults include seven categories of increasing completeness of information.
Data release of geospatial map database and structural measurements for: Geologic map of the Osage SW 7.5' quadrangle, Newton, Madison, and Carroll counties, Arkansas
This dataset accompanies publication "Geologic map of the Osage SW 7.5' quadrangle, Newton, Madison, and Carroll counties, Arkansas". Data presented here include the digital geologic database and structural measurements including joints, deformation bands, and small faults collected during field investigation. These data support the following publication: Turner, K.J., and Hudson, M.R., 2018, Geo
Filter Total Items: 13
Geologic map of the Osage SW 7.5ʹ quadrangle, Newton, Madison, and Carroll Counties, Arkansas
This map summarizes the geology of the U.S. Geological Survey Osage SW 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Physiographically, the Osage SW quadrangle is located within a transitional area between the Boston Mountains to the south, and the Springfield Plateau to the north. Geologically, the area is on the southern flank of the Ozark dome; an uplift with the olde
Geologic map of the Murray Quadrangle, Newton County, Arkansas
This map summarizes the geology of the Murray quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area is on the southern flank of the Ozark dome, an uplift that has the oldest rocks exposed at its center, in Missouri. Physiographically, the Murray quadrangle is within the Boston Mountains, a high plateau region underlain by Pennsylvanian sandstones and shales. Valleys
Geologic map of the west-central Buffalo National River region, northern Arkansas
This map summarizes the geology of the west-central Buffalo National River region in the Ozark Plateaus region of northern Arkansas. Geologically, the region lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the map area spans the Springfield Plateau, a topographic surface generally held up by Mississippian cherty limest
Geologic map of the Cochiti Dam quadrangle, Sandoval County, New Mexico
The Cochiti Dam quadrangle is located in the southern part of the Española Basin and contains sedimentary and volcanic deposits that record alluvial, colluvial, eolian, tectonic and volcanic processes over the past seventeen million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The primary mapping responsibilities were as follows: Dethier mapped the surficial deposi
Geologic map of the Cochiti Dam quadrangle, Sandoval County, New Mexico
The Cochiti Dam quadrangle is located in the southern part of the Española Basin and contains sedimentary and volcanic deposits that record alluvial, colluvial, eolian, tectonic and volcanic processes over the past seventeen million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The primary mapping responsibilities were as follows: Dethier mapped the surficial deposi
Geologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico
The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the U
Geologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico
The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the U
Geologic map of the Maumee quadrangle, Searcy and Marion Counties, Arkansas
This map summarizes the geology of the Maumee 7.5-minute quadrangle in northern Arkansas. The map area is in the Ozark plateaus region on the southern flank of the Ozark dome. The Springfield Plateau, composed of Mississippian cherty limestone, overlies the Salem Plateau, composed of Ordovician carbonate and clastic rocks, with areas of Silurian rocks in between. Erosion related to the Buffalo Riv
Geologic map of the St. Joe quadrangle, Searcy and Marion Counties, Arkansas
This map summarizes the geology of the St. Joe 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the St. Joe quadrangle lies within the Springfield Plateau, a topographic surface generally held up by Mississippian cherty limes
Geologic Map of the Boxley Quadrangle, Newton and Madison Counties, Arkansas
This map summarizes the geology of the Boxley 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the Boxley quadrangle lies within the Boston Mountains, a high plateau region underlain by Pennsylvanian sandstones and shales. Va
Geologic map of the Western Grove quadrangle, northwestern Arkansas
This map summarizes the geology of the Western Grove 7.5-minute quadrangle in northern Arkansas that is located on the southern flank of the Ozark dome, a late Paleozoic regional uplift. The exposed bedrock of this map area comprises approximately 1,000 ft of Ordovician and Mississippian carbonate and clastic sedimentary rocks that have been mildly folded and broken by faults. A segment of the Buf
Geologic map of the Hasty Quadrangle, Boone and Newton Counties, Arkansas
This digital geologic map compilation presents new polygon (for example, geologic map unit contacts), line (for example, fault, fold axis, and structure contour), and point (for example, structural attitude, contact elevations) vector data for the Hasty 7.5-minute quadrangle in northern Arkansas. The map database, which is at 1:24,000-scale resolution, provides geologic coverage of an area of cur
Filter Total Items: 24
Late Paleozoic flexural extension and overprinting shortening in the southern Ozark dome, Arkansas, USA: Evolving fault kinematics in the foreland of the Ouachita orogen
Faults and folds on the southern flank of the Ozark dome in northern Arkansas, USA, record flexural extension in a foreland area followed by shortening in response to the late Paleozoic Ouachita orogeny. Map-scale structures and an analysis of fault-slip data collected systematically during geologic mapping demonstrate that most deformation in the area accommodated north-south extension as the sou
A paleomagnetic age estimate for the draining of ancient Lake Alamosa, San Luis Valley, south-central Colorado, U.S.A.
In September 2009, a 99.4-m (326-ft) deep well was drilled proximal to Great Sand Dunes National Park and Preserve to explore the history and subsurface geology of the San Luis Valley, Colorado. Of particular interest was deciphering the evolution of ancient Lake Alamosa, which filled much of the San Luis Valley in the Pliocene and Pleistocene. Thick intervals of massive clay, recovered at the wel
The effect of lithology on valley width, terrace distribution, and coarse sediment provenance in a tectonically stable catchment with flat-lying stratigraphy
How rock resistance or erodibility affects fluvial landforms and processes is an outstanding question in geomorphology that has recently garnered attention owing to the recognition that the erosion rates of bedrock channels largely set the pace of landscape evolution. In this work, we evaluate valley width, terrace distribution, and sediment provenance in terms of reach scale variation in litholog
Geologic and geophysical models for Osage County, Oklahoma, with implications for groundwater resources
This report summarizes a three-dimensional (3-D) geologic model that was constructed to provide a framework to investigate groundwater resources of the Osage Nation in northeastern Oklahoma. This report also presents an analysis of an airborne electromagnetic (AEM) survey that assessed the spatial variation of electrical resistivity to depths as great as 300 meters in the subsurface. The report an
Introduction in New perspectives on Rio Grande rift basins: from tectonics to groundwater
Basins of the Rio Grande rift have long been studied both for their record of rift development and for their potential as host of natural resources. Early workers described the basin geomorphology and the character of infilling sediments (e.g. Siebenthal, 1910; Bryan, 1938; Speigel and Baldwin, 1963), and subsequent research compilations provided general stratigraphic and tectonic overviews of ri
Oblique transfer of extensional strain between basins of the middle Rio Grande rift, New Mexico: Fault kinematic and paleostress constraints
The structural geometry of transfer and accommodation zones that relay strain between extensional domains in rifted crust has been addressed in many studies over the past 30 years. However, details of the kinematics of deformation and related stress changes within these zones have received relatively little attention. In this study we conduct the first-ever systematic, multi-basin fault-slip measu
Geophysical constraints on Rio Grande rift structure and stratigraphy from magnetotelluric models and borehole resistivity logs, northern New Mexico
Two- and three-dimensional electrical resistivity models derived from the magnetotelluric method were interpreted to provide more accurate hydrogeologic parameters for the Albuquerque and Española Basins. Analysis and interpretation of the resistivity models are aided by regional borehole resistivity data. Examination of the magnetotelluric response of hypothetical stratigraphic cases using resist
Aeromagnetic anomalies over faulted strata
High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift in
Three-dimensional geologic model of the southeastern Espanola Basin, Santa Fe County, New Mexico
This multimedia model and report show and describe digital three-dimensional faulted surfaces and volumes of lithologic units that confine and constrain the basin-fill aquifers within the Espanola Basin of north-central New Mexico. These aquifers are the primary groundwater resource for the cities of Santa Fe and Espanola, six Pueblo nations, and the surrounding areas. The model presented in this
Guides to understanding the aeromagnetic expression of faults in sedimentary basins: Lessons learned from the central Rio Grande rift, New Mexico
High-resolution aeromagnetic data acquired over several basins in the central Rio Grande rift, north-central New Mexico, prominently display low-amplitude (5–15 nT) linear anomalies associated with faults that offset basin-fill sediments. The linear anomalies give an unparalleled view of concealed faults within the basins that has significant implications for future basin studies. These implicatio
Three-Dimensional Geologic Framework Model for a Karst Aquifer System, Hasty and Western Grove Quadrangles, Northern Arkansas
Understanding ground-water flow in a karst aquifer benefits from a detailed conception of the three-dimensional (3D) geologic framework. Traditional two-dimensional products, such as geologic maps, cross-sections, and structure contour maps, convey a mental picture of the area but a stronger conceptualization can be achieved by constructing a digital 3D representation of the stratigraphic and stru
Regional Survey of Structural Properties and Cementation Patterns of Fault Zones in the Northern Part of the Albuquerque Basin, New Mexico - Implications for Ground-Water Flow
Motivated by the need to document and evaluate the types and variability of fault zone properties that potentially affect aquifer systems in basins of the middle Rio Grande rift, we systematically characterized structural and cementation properties of exposed fault zones at 176 sites in the northern Albuquerque Basin. A statistical analysis of measurements and observations evaluated four aspects o
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Ozark Dome-Arkoma Basin-Ouachita Transect
The Ozark Dome-Arkoma Basin-Ouachita Transect (ODABOuT) project examines the three-dimensional geology of a transect of the southern orogenic margin of North America in its best surface exposure in western Arkansas. The Ozark Dome and Arkoma Basin represent a foreland uplift and foreland basin that formed as a result of the impinging Ouachita orogenic belt. Understanding the geometry and evolution...Geologic Mapping Studies at Buffalo National River, Northern Arkansas
Detailed geologic mapping is being conducted by the USGS in and adjacent to the Buffalo National River, a park administered by the National Park Service, to better understand and characterize the natural resources and associated ecosystems of this area within the Ozark Plateau region. General-purpose geologic maps are created to provide a framework for a host of natural resource, natural history... - Data
Literature compilation of paleocurrent data from the Late Paleozoic Ouachita orogen, Oklahoma-Arkansas, U.S.A.
This digital geospatial compilation gathered paleoflow indicators from current-formed sedimentary structures throughout the Paleozoic Ozark uplift, Arkoma foreland basin, and Ouachita fold-thrust-belt of eastern Oklahoma and western Arkansas from existing publications. This dataset consists of unidirectional and bidirectional paleocurrents observed from a variety of bedform types represented by apFault data collected between 1996 and 2019 from the Buffalo River watershed area, northern Arkansas
Information on the locations and characteristics of faults were collected while conducting fieldwork between 1996 and 2019 in support of geologic mapping in the Buffalo River watershed area of northern Arkansas. A total of 1274 entries on faults were recorded at 452 sites. The observations associated with faults include seven categories of increasing completeness of information.Data release of geospatial map database and structural measurements for: Geologic map of the Osage SW 7.5' quadrangle, Newton, Madison, and Carroll counties, Arkansas
This dataset accompanies publication "Geologic map of the Osage SW 7.5' quadrangle, Newton, Madison, and Carroll counties, Arkansas". Data presented here include the digital geologic database and structural measurements including joints, deformation bands, and small faults collected during field investigation. These data support the following publication: Turner, K.J., and Hudson, M.R., 2018, Geo - Maps
Filter Total Items: 13
Geologic map of the Osage SW 7.5ʹ quadrangle, Newton, Madison, and Carroll Counties, Arkansas
This map summarizes the geology of the U.S. Geological Survey Osage SW 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Physiographically, the Osage SW quadrangle is located within a transitional area between the Boston Mountains to the south, and the Springfield Plateau to the north. Geologically, the area is on the southern flank of the Ozark dome; an uplift with the oldeGeologic map of the Murray Quadrangle, Newton County, Arkansas
This map summarizes the geology of the Murray quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area is on the southern flank of the Ozark dome, an uplift that has the oldest rocks exposed at its center, in Missouri. Physiographically, the Murray quadrangle is within the Boston Mountains, a high plateau region underlain by Pennsylvanian sandstones and shales. ValleysGeologic map of the west-central Buffalo National River region, northern Arkansas
This map summarizes the geology of the west-central Buffalo National River region in the Ozark Plateaus region of northern Arkansas. Geologically, the region lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the map area spans the Springfield Plateau, a topographic surface generally held up by Mississippian cherty limestGeologic map of the Cochiti Dam quadrangle, Sandoval County, New Mexico
The Cochiti Dam quadrangle is located in the southern part of the Española Basin and contains sedimentary and volcanic deposits that record alluvial, colluvial, eolian, tectonic and volcanic processes over the past seventeen million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The primary mapping responsibilities were as follows: Dethier mapped the surficial deposiGeologic map of the Cochiti Dam quadrangle, Sandoval County, New Mexico
The Cochiti Dam quadrangle is located in the southern part of the Española Basin and contains sedimentary and volcanic deposits that record alluvial, colluvial, eolian, tectonic and volcanic processes over the past seventeen million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The primary mapping responsibilities were as follows: Dethier mapped the surficial deposiGeologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico
The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the UGeologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico
The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the UGeologic map of the Maumee quadrangle, Searcy and Marion Counties, Arkansas
This map summarizes the geology of the Maumee 7.5-minute quadrangle in northern Arkansas. The map area is in the Ozark plateaus region on the southern flank of the Ozark dome. The Springfield Plateau, composed of Mississippian cherty limestone, overlies the Salem Plateau, composed of Ordovician carbonate and clastic rocks, with areas of Silurian rocks in between. Erosion related to the Buffalo RivGeologic map of the St. Joe quadrangle, Searcy and Marion Counties, Arkansas
This map summarizes the geology of the St. Joe 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the St. Joe quadrangle lies within the Springfield Plateau, a topographic surface generally held up by Mississippian cherty limesGeologic Map of the Boxley Quadrangle, Newton and Madison Counties, Arkansas
This map summarizes the geology of the Boxley 7.5-minute quadrangle in the Ozark Plateaus region of northern Arkansas. Geologically, the area lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the Boxley quadrangle lies within the Boston Mountains, a high plateau region underlain by Pennsylvanian sandstones and shales. VaGeologic map of the Western Grove quadrangle, northwestern Arkansas
This map summarizes the geology of the Western Grove 7.5-minute quadrangle in northern Arkansas that is located on the southern flank of the Ozark dome, a late Paleozoic regional uplift. The exposed bedrock of this map area comprises approximately 1,000 ft of Ordovician and Mississippian carbonate and clastic sedimentary rocks that have been mildly folded and broken by faults. A segment of the BufGeologic map of the Hasty Quadrangle, Boone and Newton Counties, Arkansas
This digital geologic map compilation presents new polygon (for example, geologic map unit contacts), line (for example, fault, fold axis, and structure contour), and point (for example, structural attitude, contact elevations) vector data for the Hasty 7.5-minute quadrangle in northern Arkansas. The map database, which is at 1:24,000-scale resolution, provides geologic coverage of an area of cur - Publications
Filter Total Items: 24
Late Paleozoic flexural extension and overprinting shortening in the southern Ozark dome, Arkansas, USA: Evolving fault kinematics in the foreland of the Ouachita orogen
Faults and folds on the southern flank of the Ozark dome in northern Arkansas, USA, record flexural extension in a foreland area followed by shortening in response to the late Paleozoic Ouachita orogeny. Map-scale structures and an analysis of fault-slip data collected systematically during geologic mapping demonstrate that most deformation in the area accommodated north-south extension as the souA paleomagnetic age estimate for the draining of ancient Lake Alamosa, San Luis Valley, south-central Colorado, U.S.A.
In September 2009, a 99.4-m (326-ft) deep well was drilled proximal to Great Sand Dunes National Park and Preserve to explore the history and subsurface geology of the San Luis Valley, Colorado. Of particular interest was deciphering the evolution of ancient Lake Alamosa, which filled much of the San Luis Valley in the Pliocene and Pleistocene. Thick intervals of massive clay, recovered at the welThe effect of lithology on valley width, terrace distribution, and coarse sediment provenance in a tectonically stable catchment with flat-lying stratigraphy
How rock resistance or erodibility affects fluvial landforms and processes is an outstanding question in geomorphology that has recently garnered attention owing to the recognition that the erosion rates of bedrock channels largely set the pace of landscape evolution. In this work, we evaluate valley width, terrace distribution, and sediment provenance in terms of reach scale variation in lithologGeologic and geophysical models for Osage County, Oklahoma, with implications for groundwater resources
This report summarizes a three-dimensional (3-D) geologic model that was constructed to provide a framework to investigate groundwater resources of the Osage Nation in northeastern Oklahoma. This report also presents an analysis of an airborne electromagnetic (AEM) survey that assessed the spatial variation of electrical resistivity to depths as great as 300 meters in the subsurface. The report anIntroduction in New perspectives on Rio Grande rift basins: from tectonics to groundwater
Basins of the Rio Grande rift have long been studied both for their record of rift development and for their potential as host of natural resources. Early workers described the basin geomorphology and the character of infilling sediments (e.g. Siebenthal, 1910; Bryan, 1938; Speigel and Baldwin, 1963), and subsequent research compilations provided general stratigraphic and tectonic overviews of riOblique transfer of extensional strain between basins of the middle Rio Grande rift, New Mexico: Fault kinematic and paleostress constraints
The structural geometry of transfer and accommodation zones that relay strain between extensional domains in rifted crust has been addressed in many studies over the past 30 years. However, details of the kinematics of deformation and related stress changes within these zones have received relatively little attention. In this study we conduct the first-ever systematic, multi-basin fault-slip measuGeophysical constraints on Rio Grande rift structure and stratigraphy from magnetotelluric models and borehole resistivity logs, northern New Mexico
Two- and three-dimensional electrical resistivity models derived from the magnetotelluric method were interpreted to provide more accurate hydrogeologic parameters for the Albuquerque and Española Basins. Analysis and interpretation of the resistivity models are aided by regional borehole resistivity data. Examination of the magnetotelluric response of hypothetical stratigraphic cases using resistAeromagnetic anomalies over faulted strata
High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift inThree-dimensional geologic model of the southeastern Espanola Basin, Santa Fe County, New Mexico
This multimedia model and report show and describe digital three-dimensional faulted surfaces and volumes of lithologic units that confine and constrain the basin-fill aquifers within the Espanola Basin of north-central New Mexico. These aquifers are the primary groundwater resource for the cities of Santa Fe and Espanola, six Pueblo nations, and the surrounding areas. The model presented in thisGuides to understanding the aeromagnetic expression of faults in sedimentary basins: Lessons learned from the central Rio Grande rift, New Mexico
High-resolution aeromagnetic data acquired over several basins in the central Rio Grande rift, north-central New Mexico, prominently display low-amplitude (5–15 nT) linear anomalies associated with faults that offset basin-fill sediments. The linear anomalies give an unparalleled view of concealed faults within the basins that has significant implications for future basin studies. These implicatioThree-Dimensional Geologic Framework Model for a Karst Aquifer System, Hasty and Western Grove Quadrangles, Northern Arkansas
Understanding ground-water flow in a karst aquifer benefits from a detailed conception of the three-dimensional (3D) geologic framework. Traditional two-dimensional products, such as geologic maps, cross-sections, and structure contour maps, convey a mental picture of the area but a stronger conceptualization can be achieved by constructing a digital 3D representation of the stratigraphic and struRegional Survey of Structural Properties and Cementation Patterns of Fault Zones in the Northern Part of the Albuquerque Basin, New Mexico - Implications for Ground-Water Flow
Motivated by the need to document and evaluate the types and variability of fault zone properties that potentially affect aquifer systems in basins of the middle Rio Grande rift, we systematically characterized structural and cementation properties of exposed fault zones at 176 sites in the northern Albuquerque Basin. A statistical analysis of measurements and observations evaluated four aspects o