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New measurements of ongoing subsidence of land proximal to the city of New Orleans, Louisiana, and including areas around the communities of Norco and Lutcher upriver along the Mississippi are reported. The rates of vertical motion are derived from interferometric synthetic aperture radar (InSAR) applied to Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data acquired on 16 June 2009 and 2 July 2012. The subsidence trends are similar to those reported for 2002–2004 in parts of New Orleans where observations overlap, in particular in Michoud, the 9th Ward, and Chalmette, but are measured at much higher spatial resolution (6 m). The spatial associations of cumulative surface movements suggest that the most likely drivers of subsidence are groundwater withdrawal and surficial drainage/dewatering activities. High subsidence rates are observed localized around some major industrial facilities and can affect nearby flood control infrastructure. Substantial subsidence is observed to occur rapidly from shallow compaction in highly localized areas, which is why it could be missed in subsidence surveys relying on point measurements at limited locations.

Catastrophic sinkholes are formed through the collapse of natural or human-made subterranean caverns, and are common in areas with evaporite and carbonate rock. Despite their danger, advance warning of these events is rare. We report a measurement of precursory surface deformation of as much as 260 mm, derived with interferometric synthetic aperture radar (InSAR) and evident over a month before surface collapse, at the site of the Bayou Corne, Louisiana (USA) sinkhole that formed in August 2012. Data collected by the airborne Uninhabited Aerial Vehicle SAR (UAVSAR) instrument were used for the study. Analysis of data acquired from two flight tracks with near-opposing imaging geometries reveal a deformation pattern consistent with compressive loading at the surface due to loss of support from a subterranean cavity collapse related to Texas Brine Oxy Geismar Well #3. The precursor deformation was nearly entirely horizontal, i.e., oriented along the surface, and manifested as movement of surface material toward the location where the sinkhole later formed. The sinkhole formed in the area with the largest gradient in surface strain, but did not cover the full extent of the precursory deformation detected with radar. This work suggests that InSAR data collected operationally for hazard monitoring could, in some cases, identify sinkhole development before surface collapse, and decrease subsequent danger to people and property.

Summary Survey contact rates differ across countries. However, to date the reasons for these cross-country differences have not been identified. Differences can be due to differences in survey characteristics, differences in population characteristics and differences in processes, i.e. in the association between the first and second reasons and contact propensity. The paper investigates correlates of contact by decomposing cross-country differences in predicted mean contact propensities into these three components. The findings explain which fieldwork strategies and population characteristics are related to cross-country differences in contact rates. The analyses distinguish factors explaining within-country contact propensity from factors explaining cross-country differences. We demonstrate the suitability of decomposition methods for analysing group differences in survey outcomes.

The use of synthetic aperture radar (SAR) imagery collected by the NASA AirSAR platform to detect archaeological site location on San Clemente Island, one of the Southern Channel Islands, has been described in several publications. Here we provide a concise review of the use of SAR for that purpose, as well as a description of how a precise surface model also generated by SAR data was used to examine the spatial distribution of sites by means of viewshed modeling. Results of the direct detection model are evaluated using gain statistics that make use of a recently completed 100% survey of all accessible areas on San Clemente Island. Viewshed analyses generated by use of the surface model suggest a number of economic and ideological factors that might have influenced the distribution of archaeological sites on the island. Among these are intervisibility among locations on both San Clemente Island and nearby Santa Catalina Island that provided the means by which to coordinate crucial substance activities, such as hunting sea mammals, and reinforced the social relationships that were essential to such activities.

Archaeology can provide insight into interactions of climate change and human activities in sensitive areas such as the Sahara, to the benefit of both disciplines. Such analyses can help set bounds on climate change projections, perhaps identify elements of tipping points, and provide constraints on models. The opportunity exists to more precisely constrain the relationship of natural solar and climate interactions, improving understanding of present and future anthropogenic forcing. We are beginning to explore the relationship of human occupation of the Sahara and long-term solar irradiance variations synergetic with changes in atmospheric-ocean circulation patterns. Archaeological and climate records for the last 12 K years are gaining adequate precision to make such comparisons possible. We employ a range of climate records taken over the globe (e.g. Antarctica, Greenland, Cariaco Basin, West African Ocean cores, records from caves) to identify the timing and spatial patterns affecting Saharan climate to compare with archaeological records. We see correlation in changing ocean temperature patterns ∼ contemporaneous with drying of the Sahara ∼6K years BP. The role of radar images and other remote sensing in this work includes providing a geographically comprehensive geomorphic overview of this key area. Such coverage is becoming available from the Japanese PALSAR radar system (Palliou, et. al., 2007), which can guide fieldwork to collect archaeological and climatic data to further constrain the climate change chronology and link to models. Our initial remote sensing efforts concentrate on the Gilf Kebir area of Egypt.

Previously unknown strike-slip and normal faults in the central and eastern Mojave Desert have been revealed on Landsat Thematic Mapper images enhanced by four-component processing. This method provides color images on which lithologies are discriminated by their contrasting absorption and reflection, primarily at infrared wavelengths and particularly with regard to their ferric iron, ferrous iron, and hydroxyl contents, while retaining landform depiction. These discriminants represent a new type of geophysical display for geologic mapping in regions of well-exposed bedrock. Faults are revealed on the images by abrupt spectral and textural contrasts that coincide with aligned topographic features. The newly discovered faults form part of an extensive regional network of right shear that connects faults in the Death Valley region with the San Andreas fault system. They support a heterogeneous strain model for late Cenozoic tectonic evolution of the region. Regional structural relations indicate a westward migration of the locus of strain through time. Some of the newly identified faults bound blocks that have experienced contrasting rotational histories since early Miocene time.

A location that likely inspired some elements of legendary accounts of the “lost city” of Ubar has been found at the edge of the Arabian Peninsula’s Empty Quarter at the village of Ash Shisr in modern day Oman. The site consists of the remains of a central fortress surrounding a well. Artifacts from as far away as Persia, Rome, and Greece are found, indicating a long period of far-flung trade through this isolated desert location. More recent work in Oman and Yemen indicates this fortress is the easternmost remains of a series of desert caravansaries that supported incense trade. Legend was that Ubar perished in a sandstorm as divine punishment for wicked living. Actually, much of the fortress collapsed into the sinkhole that hosted the well, perhaps undermined by ground water withdrawal used to irrigate the surrounding oasis. Less fanciful interpretation of legendary and other accounts clearly indicates “Ubar” was actually a region—the “Land of the Iobaritae” identified by Ptolemy. Desert trade was probably abandoned because of three primary factors: frankincense diminished in importance with the conversion of the Roman Empire to Christianity, desert ground-water levels continued to fall and the oases dried up, and reliable sea transportation was developed. The archaeological site was located, and its importance recognized, by an unusual combination of historical research and application of space technology in support of traditional archaeology. The site was known earlier but its significance unappreciated, as it was never studied in adequate detail. The archaeological importance of the site is supported through regional context provided by carefully enhanced Landsat Thematic Mapper (TM) and other satellite imagery that shows a discontinuous network of trails that converge at Shisr. Some of these trails are demonstrably old as they pass beneath sand dunes 100 m tall. Thus the desert environment can preserve ancient evidence of human occupation detectable in remote sensing data. Image analysis further shows no evidence of major undocumented sites in this desert region (e.g. the “Ubar” of legend). The interdisciplinary nature of this work demonstrates the significant and still underutilized potential of using remote sensing and GIS technology in support of traditional archaeology.

Protocols for archaeological inventory of large areas using synthetic aperture radar (SAR) are presented here. They were developed during a 2002–2005 research project sponsored by a Department of Defense Strategic Environmental Research and Development Program Research Project (SERDP CS-1260) on San Clemente Island, California. Archaeological evidence has established that San Clemente Island has been occupied for almost 10,000 years. Some protocols can also be used with other aerial and satellite datasets, such as those acquired by multispectral sensors. Protocols rely upon algorithms to merge data from multiple flight lines, collection of spatially precise ground data with which to develop signatures, knowledge of site morphology, and elegant statistical treatments of sensing-device return values to automate the development of site signatures (in contrast to using the “trained eye” of remote sensing experts). The Introduction of the article presents the study rationale, SAR basics essential to this research, study-site description, and an overview of fieldwork done. The Results section details eight SAR protocols that were developed: data collection, including look angles, flight lines, and choice of band and polarization; data processing and image production, including orthorectification and the merging of data from multiple flight lines; image post-processing, including statistical techniques and iteration of images; corroborative use of multispectral datasets; spatial modeling; procedures for incorporation into and analysis with GIS; establishment of statistically based site signatures; and procedures for ground verification. In the Discussion, the authors extend some of their findings to archaeological research at San Clemente Island and beyond. The article concludes by highlighting some important management implications for the use of SAR as an archaeological evaluation tool for sizeable land areas. In environments not too dissimilar to those on San Clemente Island, these protocols can produce planning level inventories much more rapidly and inexpensively than field methods commonly used at present can.

Remotely sensed imagery can be applied to neotectonic studies in ways quite different from its traditional use, the generation of enhanced spectral maps. Large neotectonic motions can be visually observed, seismogenic strain fields can be mapped, and the imagery can be combined with other geophysical data sets for synergistic, real-time exploration of multi-dimensional relationships. >

Over the last fifteen years, an unusual combination of space technologies coupled with traditional archaeology has given insight into the ancient southern Arabian frankincense trade, including the discovery of the lost "city" of Ubar in present day Oman. Continued research indicates a series of desert caravansaries to the west in modern Yemen. Pliny, the ancient Roman historian, reports that there were "octomansiones" (eight fortresses, or mansions) along the desert frankincense trade route. The authors present work seeks to document this, and illuminate the poorly known civilization which supported frankincense trade. They presently have Landsat Thematic Mapper (TM) coverage of most of southern Arabia. They also have geographically discontinuous SIR-C and ERS coverage. At present they also have publicly released quicklook SRTM data for the border area between Yemen and Oman, and eagerly await full coverage with SRTM topographic data. Topographic data will provide critical insight into trade routes and fortresses with regards to water sources and routes from the coast and mountains, where people lived, to the interior desert. Given the nature of this research, comprehensive geographic coverage provided by SRTM and Landsat are a fundamental requirement.

The location of the legendary city of Ubar, a desert caravansary which supported the ancient and lucrative frankincense trade, has likely been found at the edge of the Arabian Peninsula's Empty Quarter in modern day Oman. Legend was that Ubar perished in a sandstorm as divine punishment for wicked living. Actually, much of the fortress collapsed into a sinkhole, perhaps undermined by extensive ground water withdrawal used to irrigate the surrounding oasis. The archaeological site was located by an unusual combination of historical research and the application of space technology in support of traditional archaeology.

A Sagnac interferometric based strain sensor has the potential to measure strain of less than 100 microns over distances of 10 km or more. By incorporating these strain sensors into telecommunication grade fiber otic cable it would be possible to monitor earth movement to high accuracy over very long links at low cost on a continual basis. This technique would be extremely complementary to systems based on the Global Positioning Satellite and Satellite based radar imaging. The potential exists for incorporating the system directly into the local, regional, and national fiber optic telecommunication infrastructure, which would for the first time allow widespread data on earth movement to be obtained. This information would be useful in studying precursory deformation related to earthquake and volcanic activity, landslides, movement of land due to river outflows, and other earth movement features that directly impact the environment. This system could be used to reduce risks in hazardous waste site areas, to monitor strain o power and telecommunication lines, to monitor potential damage due to earth movement of utilities and buildings, and the movement of oil platforms at sea due to river outflows reducing oil spillage risks.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of satellite-derived imagery for measuring subresolution horizontal terrain displacments associated with present-day earthquakes is discussed with reference to data from the French SPOT satellite whose sensor array provides 10-m panchromatic imagery. The measured terrain displacements can be up to several meters, but usually no more than 6-8 m even for major earthquakes. The general approach is to spatially match the after image to the before image at each point on a half-kilometer grid by iteratively interpolating one and testing its correlation with the other. The discussion covers the basic algorithm, results of initial tests, error types and limitations, and future work.

Undocumented late Miocene and younger strike-slip and normal faults that extend up to 25 km in the eastern and central Mojave Desert Block have been detected and mapped in LANDSAT thematic mapper images. The faults are located in the Bristol Mountains, Cady Mountains, and Alvord Mountain areas. Additional strike-slip faults detected in the adjacent Fort Irwin Military Reservation have yet to be verified in the field. The images were processed to enhance the spectral responses without suppressing topography. The faults are detected on the images because of spectral contrasts mostly at wavelengths longer than the visible. The newly detected faults form part of a complex regional network of right shear that connects faults in the southern Death Valley region with the San Andreas Fault System. Some of the newly identified faults bound blocks that have experienced different Neogene rotational histories. These faults have likely served to accommodate those motions. Structural relations along the faults suggest at least two intervals of movement. In the Bristol Mountains, east of Broadwell Lake, the faults are overlain by unconsolidated alluvial fan debris (late Quaternary ) and are probably inactive. In the Cady Mountains to the west and south, the faults cut all deposits andmore » are currently active. The discovery of these undocumented faults indicates that existing knowledge of fault distribution in the area is incomplete and not fully representative. This has important implications for seismic risk assessment and for determining the suitability of the desert for increased use by man.« less

Undocumented late Miocene and younger strike-slip and normal faults that extend up to 25 km in the eastern, and northeastern Mojave Desert block have been detected and mapped using Landsat thematic mapper (TM), SPOT panchromatic, and synthetic-aperture radar (SAR) images. The faults are located in the Bristol Mountains, Cady Mountains, Alvord Mountain, and Granite Mountains (Fort Irwin military reservation) areas. Some faults are perceived on the TM images because of spectral contrasts primarily at infrared wavelengths. Other faults are highlighted on SPOT panchromatic and radar images because of topographic contrasts. Corregistration of enhanced TM/SPOT panchromatic data maximizes both spectral and topographic information in the images. The newly detected faults form part of a complex regional network of right shear in eastern California that connects faults in the southern Death Valley region with the San Andreas fault system. Structural relations along. the faults suggest at least two intervals of movement and a westward migration of the locus of strain in the southern Mojave. In the Bristol Mountains east of Broadwell Lake, the faults are overlain by undisturbed Pleistocene alluvial fan deposits and are probably inactive. In contrast, the area to the west (Cady Mountains) and south contains faults that cut all deposits and is seismically active. Some faults in the Cady Mountains bound blocks that have experienced differing rotational histories since middle Miocene time. Newly identified faults in the northeastern Mojave suggest that right-slip may be more important to the overall deformation than previously reported.

Enhanced Landsat TM images were used in conjunction with field work to investigate the regional correlation of Miocene rocks in the Colorado River extensional corridor of California and Arizona. Based on field investigations, four sequences of sedimentary and volcanic strata could be recognized in the Mohave Mountains (Arizona) and the eastern Whipple Mountains (California), which display significantly different relative volumes and organization of lithologies. The four sequences were also found to have distinctive appearances on the TM image. The recognition criteria derived from field mapping and image interpretation in the Mohave Mountains and Whipple Mountains were applied to an adjacent area in which stratigraphic affinities were less well known. The results of subsequent field work confirmed the stratigraphic and structural relations suggested by the Tm image analysis.

The effects of look angle and wavelength variation in geologically applied radar images are examined and the applications of observations of these effects for the study of other planets are discussed. Seasat, SIR-A, SIR-B, and airborne radar images and multiple look angle and multiwavelength scatterometer data are used. It is found that smaller look angle radar data can provide good discrimination among certain diverse materials which are not distinguishable at larger look angles, such as subpixel fault scarps and volcanic dykes. Discriminant analyses of scatterometer data of all geological targets observed gave best results with minimum data by using all wavelengths available and small look angles. The results provide information on the nature of radar images which could be valuable in interpreting radar images of Venus.

There is a large surplus of low value black cottonwood and other hardwoods in British Columbia. Greatly improved utilization and management are needed to make effective use of B.C. hardwoods.During the past decade, in their efforts to develop an economical supply of high quality veneer logs and pulpwood, West Tree Farms has encountered and solved many operational problems. Therefore, the experience described herein should be of interest to other Canadian foresters who may be faced before long with the need to intensify forest management.Much can be learned in a short period of time. For example, after only 11 years in the field, black cottonwoods and hybrid poplars planted in 1956 either as one-year-old rooted trees or rootless trees (sets) have reached a size considered commercial in many parts of Canada. They averaged 8 inches in dbh and 70 feet in height in October, 1966.Growth and yield of black cottonwood are excellent but it is difficult to grow in nurseries and inferior in form and natural pruning when compared with 'robusta' and similar hybrid poplars. Establishment of hybrid poplars requires either very expensive site preparation and many weedings and thinning or relatively economical strip clearing and planting of either large rooted trees or sets at wide spacings. The latter is preferable in B.C.Prospects for improvement of tree growth and wood quality are excellent but, like development of effective programs for preventing and controlling losses from disease, insects, and other pests, tree improvement requires much long-term research. Research and practice should be sustained and closely related. It is to be hoped, therefore, that the Province of British Columbia will make more land available for tree farming, and that the Federal Government will support the kinds of research needed to improve the programs started by West Tree Farms and others interested in poplar cultivation.

On a Seasat radar image (23.5-cm wavelength) of the Durmid Hills in southern California, the San Andreas fault is expressed as a prominent southeast-trending tonal lineament that is bright on the southwest side and dark on the northeast side. Field investigation established that the bright signature corresponds to outcrops of the Borrego Formation, which weathers to a rough surface. The dark signature corresponds to the Lake Cahuilla sand and silt deposits which are smooth at the wavelength of the Seasat radar. These signatures and field characteristics agree with calculations of the smooth and rough radar criteria. On Landsat and Skylab images of the Durmid Hills, the Borrego and Lake Cahuilla surfaces have similar bright tones and the San Andreas fault is not detectable On a side-looking airborne radar image (0.86-cm wavelength), both the Borrego and Lake Cahuilla surfaces appear rough, which results in bright signatures on both sides of the San Andreas fault. Because of this lack of roughness contrast, the fault cannot be distinguished on the aircraft image acquired at a short radar wavelength. The wavelength of the Seasat radar system is well suited for mapping Durmid Hills geologic features that are obscure on the other remote sensing images evaluated in this report.

Three synthetic aperture radars (SARs) sponsored by NASA have been flown in space. SEASAT in 1978, SIR-A in 1981 and SIR-B in 1984. Spaceborne radar image interpretation is different from airborne radar image interpretation, principally due to the wide swath and constant image geometry. Spaceborne SAR constitutes a high precision image data set in the sense that large areas are imaged under near-uniform illumination conditions. Thus spaceborne SAR images are ideally suited to geological studies of a regional nature. For spaceborne radar images a low incidence angle is probably preferable in areas of modest topography. Multifrequency observations area also needed for certain terrain-type distinctions. Subsurface imaging can occur in arid and semi-arid terrains provided that very restrictive conditions are simultaneously met. Despite the limitations sub-surface imaging has important applications in geology, hydrology, archaeology and other disciplines. Analysis of SEASAT images of a tropical terrain (Jamaica) reveals that SEASAT can provide unique information on structure and rock-type distribution on a regional scale in an environment which is not favourable for visible sensors. Possible future NASA radar missions such as SIR-B reflight, SIR-C and Space Station will provide new data from different incidence angles, frequencies and polarizations in the coming years.

Igneous dikes buried beneath as much as 2 m of alluvium in the Mojave Desert of California were detected by the SEASAT L-band (23.5-cm wavelength) synthetic-aperture radar (SAR) in 1978. The roughness and dihedral configuration of the dikes are favorable to generation of strong radar echos. The soil-moisture levels in 1978 were likely below the critical 1% level. The other permissive conditions for radar penetration of a fine-grained and thin alluvial cover are present. Our findings suggest that subsurface features with potential tectonic or geomorphic significance may be revealed in other orbital radar images of semiarid terrains.