Southwest Edge Research Articles

Geophysical images of the creeping segment of the San Andreas fault: implications for the role of crustal fluids in the earthquake process

High-resolution magnetotelluric (MT) studies of the San Andreas fault (SAF) near Hollister, CA have imaged a zone of high fluid content flanking the San Andreas fault and extending to midcrustal depths. This zone, extending northeastward to the Calaveras fault, is imaged as several focused regions of high conductivity, believed to be the expression of tectonically bound fluid pockets separated by northeast dipping, impermeable fault seals. Furthermore, the spatial relationship between this zone and local seismicity suggests that where present, fluids inhibit seismicity within the upper crust (0–4 km). The correlation of coincident seismic and electromagnetic tomography models is used to sharply delineate geologic and tectonic boundaries. These studies show that the San Andreas fault plane is vertical below 2 km depth, bounding the southwest edge of the imaged fault-zone conductor (FZC). Thus, in the region of study, the San Andreas fault acts both as a conduit for along-strike fluid flow and a barrier for fluid flow across the fault. Combined with previous work, these results suggest that the geologic setting of the San Andreas fault gives rise to the observed distribution of fluids in and surrounding the fault, as well as the observed along-strike variation in seismicity.

Education and Propagation of Intravascular Surgery in Okinawa

Okinawa is an island located on the southwest edge of the Japanese Islands in which about 1,300,000 people live, and is an area where selfconclusion type medical treatment is desired. In this area, intravascular surgery was only performed for several cases per year until 1998. From May 1999, intravascular surgery started being performed in earnest, and 140 or more cases of intravascular surgery per year were performed in 2002. In the meantime, various measures for the propagation and development of intravascular surgery that we undertook led to the increase in the number of cases. As a result, the choice of medical treatment has increased by propagating these medical treatments, and it seems that this has contributed to the welfare of the people of Okinawa.

Nutrient and Plankton Dynamics in the NE and NW Gyres of the Subarctic Pacific Ocean

The western subarctic gyre (WSG) and the eastern Alaska Grye (AG) on each side of the subarctic North Pacific, have many similarities. In both gyres, macronutrients are generally high and chl is low, and hence both gyres are High Nitrate, Low Chlorophyll (HNLC) regions. Despite the general similarities between these two gyres, there are many important differences. The time series station established at Stn KNOT on the southwest edge of the WSG and two in situ mesoscale iron enrichment experiments at each of the gyres has provided more information on iron concentrations, the dual role of iron and silicate limitation and seasonal cycles in the gyres. There is more seasonality in many parameters at Stn KNOT than at Stn P. There is an increase in Chl and primary productivity at Stn KNOT in May followed by increased iron limitation in summer. Low DIC:NO3 ratios and high Si:NO3 ratios in the WSG, indicate lower calcification and higher diatom production than at Stn P. The sources of iron for these areas are still not clear, but horizontal transport of iron rich coastal water and vertical transport could be important sources at certain times of the year in addition to dust input. Satellite images show that chl-rich coastal waters occasionally extend to the vicinity of Stn KNOT and therefore Stn KNOT may not always represent conditions in the main part of the WSG. This review focuses mainly on a comparison of Stn KNOT and Stn P, two time series stations on the edge of two very large gyres. At present, we have a limited understanding of the temporal and spatial variability within each of these large gyres.

Characterization of suburban areas for land use planning using landscape ecological indicators derived from Ikonos-2 multispectral imagery

Very high resolution satellite images are used to derive the spatial distributions of landscape ecological metrics within suburban areas. These indicators are weighted mean patch size and lacunarity computed from thresholded normalized difference vegetation index obtained from multispectral IKONOS-2 imagery. Spatial distributions of the metrics are derived for an extensive suburban area on the southwest edge of London, U.K. Weighted mean patch size and lacunarity values have also been investigated in subimages corresponding to different kinds of suburban land cover and with different box sizes. The results indicate typical ranges of the metrics in environmentally sustainable localities. The spatial distributions of the metrics provide new insight into landscape structure, which can be exploited in land use planning and in the construction of empirical spatial planning heuristics for sustainable urban development.

Dante's orphans

WHEN YOU FLY INTO Johannesburg, South Africa, from the United States or Europe, you quickly become aware of the contrast between wealth (mostly white) and poverty (mostly black). In case you failed to notice this from the air, a drive outside the city in almost any direction takes you past miles of shanties. The most famous collection of these, Soweto, lies on the city's southwest edge. The name itself is a contraction of “southwestern township,” a place originally set aside for black miners and their families. The lure of wealth (for some) is evident to anyone aware that Johannesburg sits astride what is still the world's largest gold reef. The name of the surrounding province, Gauteng, is the Xhosa word meaning “gold.” The racial and economic contrasts here provide the only needed explanation for the fear of crime felt by people of every color and for the extraordinary safety precautions taken by the “haves.” South Africa is still imperiled by its legacy of racism and greed.

Neotectonics and Quaternary geology of the Hunter Mountain fault zone and Saline Valley region, southeastern California

The Hunter Mountain fault zone strikes northwesterly, is right-lateral strike-slip, and kinematically links the northern Panamint Valley fault zone to the southern Saline Valley fault zone. The most recent displacement of the fault is recorded in the offset of Holocene deposits along the entire length of the fault zone. Right-lateral offsets of drainage channels within Grapevine Canyon reach up to 50 to 60 m. Initial incision of the offset channels is interpreted on the basis of geomorphic and climatic considerations to have occurred approximately 15 ka. The 50 to 60 m of offset during 15 ka corresponds to a right-lateral fault slip rate of 3.3–4.0 mm/year within Grapevine Canyon. Further to the north along the Nelson Range front, the fault is composed of two sub-parallel fault strands and the fault begins to show an increased normal component of motion. A channel margin that is incised into a Holocene surface that is between 10 and 128 ka in age is offset 16–20 m, which yields a broad minimum bound on the lateral slip rate of 0.125–2.0 mm/year. The best preserved single-event displacements recorded in Holocene deposits range from 1.5 to 2.5 m. In addition to faulting within Grapevine Canyon and the main rangefront fault along the southwest edge of Saline Valley, there also exist normal fault strands within the Valley that strike northeasterly and towards Eureka Valley. The northeasterly striking normal faults in the Valley appear to be actively transferring dextral slip from the Hunter Mountain fault zone north and east onto the Furnace Creek fault zone. Separations on northerly trending, normal faults within Saline Valley yield estimates of slip rates in the hundredths of millimeters per year.

Trace gas transport and scavenging in PEM‐Tropics B South Pacific Convergence Zone convection

Analysis of chemical transport on Flight 10 of the 1999 Pacific Exploratory Mission (PEM) Tropics B mission clarifies the role of the South Pacific Convergence Zone (SPCZ) in establishing ozone and other trace gas distributions in the southwestern tropical Pacific. The SPCZ is found to be a barrier to mixing in the lower troposphere but a mechanism for convective mixing of tropical boundary layer air from northeast of the SPCZ with upper tropospheric air arriving from the west. A two‐dimensional cloud‐resolving model is used to quantify three critical processes in global and regional transport: convective mixing, lightning NOx production, and wet scavenging of soluble species. Very low NO and O3 tropical boundary layer air from the northeastern side of the SPCZ entered the convective updrafts and was transported to the upper troposphere where it mixed with subtropical upper tropospheric air containing much larger NO and O3 mixing ratios that had arrived from Australia. Aircraft observations show that very little NO appears to have been produced by electrical discharges within the SPCZ convection. We estimate that at least 90% of the HNO3 and H2O2 that would have been in upper tropospheric cloud outflow had been removed during transport through the cloud. Lesser percentages are estimated for less soluble species (e.g., <50% for CH3OOH). Net ozone production rates were decreased in the upper troposphere by ∼60% due to the upward transport and outflow of low‐NO boundary layer air. However, this outflow mixed with much higher NO air parcels on the southwest edge of the cloud, and the mixture ultimately possessed a net ozone production potential intermediate between those of the air masses on either side of the SPCZ.

Open clusters or their remnants: $\vec{B}$ and $\vec{V}$ photometry of NGC 1901 and NGC 1252

Photometry in theB andV bands is presented for the southern stellar groups NGC 1901 and NGC 1252. NGC 1901 is often described as an open cluster while NGC 1252 consists of a concentration of about 20 stars centered20 0 north of the original New General Catalogue coordinates, and at the southwest edge of the large region previously assigned to this object in the literature. NGC 1901 has a clear main sequence and shares similarities with the Hyades. We derive a reddening value E(B V )=0 :04, a distance from the Sund =0 :45 kpc (Z = 0:23 kpc) and an age 0.6 0.1 Gyr. NGC 1901 is conclusively a physical system, dynamically comparable to or more evolved than the Hyades. The colour-magnitude diagram of NGC 1252 suggests a turno and main sequence, and a total of 12 probable members. We simulated the Galactic eld colour-magnitude diagram in the same direction and found it to be a poor match to NGC 1252, suggesting that NGC 1252 is not a eld fluctuation. Isochrone tting to the probable members is consistent with E(B V )=0 :02, d =0 :64 kpc (Z = 0:46 kpc) and an age 3 1 Gyr. NGC 1252 cannot be ruled out as a physical group with the available data. If so, evidence is found that it is not a classical open cluster, but rather an open cluster remnant.

South Kavala Gas Field - Taphrogenetic Prinos Basin

The South Kavala gas field located at the southwest edge of the Prinos basin was discovered at the turn of 1972 -73. The basin formation started in the middle Miocene with continental deposits. Later on the sea transgressed all over the basin until the south Kavala ridge at the southern limit lifted up and transformed it to a lagoon, leading to the formation of Evaporites in upper Miocene time. At Pliocene the sea dominated again covering even the previous mentioned ridge. An unconformity exists between Miocene and Pliocene visible mainly on the basin flanks. The trapping mechanism is a combination of a roll-over anticline in front of a northeast - southwest syngenetic fault and a pinch - out of the sediment deposits to the southwest towards the South Kavala ridge. The basement itself forms an erosional high. The gas reservoir is found between two evaporitic horizons and consists mainly of sandstone, microconglomeratic alternating with shale and marl. It is of turbiditic origin forming sedimentological cycles. Individual facies A4/B2, C and E representative of the turbidite facies classification of Walker and Mutti (1973) have been recognised. The net pay thickness is small and amounts up to eleven meters. The gas consists 83% of methan, 7.5% of ethan, 1.5% of propan and around 1.5% of butan. It is free of H2S and contains condensate. As source rocks are considered the under continental and marine conditions deposited preevaporitic shales. The coal beds are also considered to be potential source rocks. The gas is of low maturity and its generation started during latest Miocene and continued through the Pliocene. The main migrations paths apparently were along the faults that cross the basin. The in place reserves are close to 1.109m3 αερίου. The field is on production from 1981 and 80% of the recoverable reserves have been already produced.

Multifrequency Studies of Bright Radio Supernova Remnants. III. X‐Ray and Radio Observations of 3C 397

Radio-bright, presumably young supernova remnants offer the opportunity of studying strong-shock physics and the nature of the interaction of ejected material with the surrounding medium. The relation between radio and X-ray morphology varies considerably among supernova remnants, with important implications for the physics of the emission processes at different wavelengths. We use Very Large Array (VLA) and Roentgen Satellite (ROSAT) images of the radio-bright supernova remnant 3C 397 (G41.1-0.3) to examine the shock structure in both thermal X-ray emission and nonthermal radio emission. The unusual rectangular morphology can be seen in VLA maps at 20 and 6 cm wavelength at a resolution of 6'' and in ROSAT HRI images. The X-ray images resemble the radio strongly, except for a small, possibly unresolved X-ray hot spot near the center. There is no variation in the X-ray hardness ratio from ROSAT Position Sensitive Proportional Counter data across the remnant, suggesting that at least between 0.4 and 2 keV the interior emission is not different in character from that in the bright shell regions. The remnant is unpolarized at 20 cm and has a mean fractional polarization of 1.5% ± 0.1% at 6 cm. The polarized flux, and polarized fraction, peak inside the remnant at a location not coincident with either an internal maximum in total-intensity radio emission or with the X-ray hot spot. Spectral index maps between 6 and 20 cm do not show any systematic differences associated with interior emission; there appears to be no plerionic or pulsar-driven component in 3C 397, at least as normally characterized by high polarization and a flat radio spectrum. Spectral index values spread about the mean by about Δα ~ 0.2, a result consistent with previous work. The steep total-intensity profile off the southwest edge of 3C 397 allows an inference of the upstream electron diffusion coefficient and implies a mean free path for electron scattering shorter than in the general interstellar medium but longer than that similarly inferred for Tycho and SN 1006. A simple analysis based on the observed X-ray flux gives an estimate of the mean density in 3C 397 of about 4 cm-3, which would also be enough to depolarize the 20 cm emission completely, as observed. The remnant age is then of order 103 yr, and the current shock velocity is about 1600 km s-1. Finally, we speculate on possible mechanisms producing the X-ray hot spot.

LAS RUINAS DE ARENAL

Las Ruinas de Arenal is a small “major” Lowland Maya center located at the southwest edge of the upper or western Belize Valley. This paper presents a preliminary description of Las Ruinas in formal, spatial, and temporal terms and reports the results of two short seasons of archaeological investigations carried out there in 1991 and 1992. Some aspects of the site's likely cultural, historical, and sociopolitical significance also are discussed.

Bicarbonate, Sulfate, and Chloride Water in a Shallow, Clastic‐Dominated Coastal Flow System, Argentina

AbstractMost of the cities southeast of Buenos Aires, Argentina, depend heavily on ground water for water supply. Whereas ground water quality is generally good in the region, economic development along the coastal plain has been constrained by high salinities.Fifty‐four wells were sampled for major ions in zones of recharge, transport and discharge in an area near La Plata, 50 km southeast of Buenos Aires. The shallow, southwest to northeast coastal flow system is >30 km long but is only 50 to 80 m thick. It consists of Plio‐Pleistocene fluvial sand overlain by Pleistocene eolian and fluvial silt and Holocene estuarine silty clay.Hydrochemical endmembers include HCO3, SO4, and Cl water. Bicarbonate‐type water includes high plain recharge water (Ca‐Na‐HCO3) that evolves through cation exchange and calcite dissolution to a high pH, pure Na‐HCO3 endmember at the southwest edge of the coastal plain. Similar Na‐HCO3 water is also found underlying recharge areas of the central coastal plain, and a lens of Ca‐HCO3 water is associated with a ridge of shell debris parallel to the coast.Mixed cation‐Cl water near the coastline represents intruded sea water that has undergone cation exchange. Chemically similar water underlying the southwest coastal plain, however, can be shown isotopically to have formed from fairly dilute solutions concentrated many times by evapotranspiration.In the central coastal plain, Na‐SO4‐Cl water (up to 17,000 mg/L SO4) underlies hummocks and, at depth, forms plumes in the subsurface. The chemical controls are dissolution of gypsum precipitated during pyrite oxidation, evapotranspiration, and calcite precipitation.This extreme diversity of water chemistry in a shallow, clastic flow system is uncommon. It is made possible by (1) the presence of oxidized, originally pyritic, but slightly permeable sediments that have been exposed to evolving geochemical and hydro‐dynamic conditions, and (2) highly focused recharge that favors the development of fresh water bodies underlying recharge zones and stagnant, evaporated water underlying other areas.

A preliminary study on quaternary glacial landforms in Mt.Ma’an

Mt.Ma’an (4288 m) is the highest mountain in the southwest edge of Sichuan Basin. It is situated to the south of the Dadu River. The geographic coordinates are: 28°58′N, 102°55′E. There are six peaks over 4000 m in elevation. Many quaternary glacial landforms in this mountain have been discovered. It’s a typical example of fossil glacial landform in the east China. Its glacial stages are the last glaciation (Q 3 3 ) and the neoglaciation (Q 4 3 ). Mt. Ma’an and Mt. Luoji (4359 m) are similar in the fossil glacial landforms, but there are still some differences between them. For example, the ratio between the direct difference and the minus difference is different.

Age of the Lancefield megafauna: A reappraisal

The Lancefield megafauna site is located on the southwest edge of the small town of Lancefield, 70 km NNE of Melbourne. The site is located in a swamp, a depression (possibly formed by a collapsed lava tunnel) which is almost surrounded by weathered Pliocene basalts which have formed a laterite cap. A natural spring flow under this cap emerges at the swamp and the water then drains into Deep Creek, a tributary of the Maribyrnong River. Three fossil megafaunal assemblages occur at Lancefield. The original discovery of 1843, now known as the Mayne Site, was the focus of investigations in the nineteenth-century and again in 1991 (van Huet 1993). The South Site, found in 1983, has been excavated three times since the early 1980s, most recently by van Huet in 1991 (van Huet 1994). The Classic Site was discovered in 1973 and was the focus of major investigations in 1975-76 (Horton 1976; Ladd 1976; Gillespie et al. 1978; Horton and Samuel 1978). Â

Two‐dimensional seismic image of the San Andreas Fault in the Northern Gabilan Range, central California: Evidence for fluids in the fault zone

A joint inversion for two‐dimensional P‐wave velocity (Vp), P‐to‐S velocity ratio (Vp/Vs), and earthquake locations along the San Andreas fault (SAF) in central California reveals a complex relationship among seismicity, fault zone structure, and the surface fault trace. A zone of low Vp and high Vp/Vs lies beneath the SAF surface trace (SAFST), extending to a depth of about 6 km. Most of the seismic activity along the SAF occurs at depths of 3 to 7 km in a southwest‐dipping zone that roughly intersects the SAFST, and lies near the southwest edge of the low Vp and high Vp/Vs zones. Tests indicate that models in which this seismic zone is significantly closer to vertical can be confidently rejected. A second high Vp/Vs zone extends to the northeast, apparently dipping beneath the Diablo Range. Another zone of seismicity underlies the northeast portion of this Vp/Vs high. The high Vp/Vs zones cut across areas of very different Vp values, indicating that the high Vp/Vs values are due to the presence of fluids, not just lithology. The close association between the zones of high Vp/Vs and seismicity suggests a direct involvement of fluids in the faulting process.

WSRT and VLA Observations of the 6 Centimeter and 2 Centimeter LInes of H 2CO in the Direction of W3

view Abstract Citations (8) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS WSRT and VLA Observations of the 6 Centimeter and 2 Centimeter LInes of H 2CO in the Direction of W3 Dickel, Helene R. ; Goss, W. Miller ; Condon, G. R. Abstract Formaldehyde absorption toward the H ii regions in W3 has been imaged at 6 cm with the Westerbork Synthesis Radio Telescope and at 2 cm with the Very Large Array with an angular resolution of ∼5" and a velocity resolution of ∼0.6 km s-1. The opacities in both transitions are low, ranging between 0.05 and 0.3. The LSR velocities are around -39 km s-1 toward the eastern component of the molecular core which includes the H II regions W3 A and W3 B and between -45 and -42 km s-1 toward the western component which includes W3 C and W3 D. The typical line widths are 1-3 km s-1 except toward the H II region W3 D (FWHM ∼5 km s-1). For this source, a "champagne flow" at the edge of the molecular cloud may explain both the wide formaldehyde lines and the gradient in the recombination lines. Typical molecular hydrogen densities are ∼105 cm-3, in agreement with earlier estimates from observations of other molecules. The abundance of formaldehyde relative to molecular hydrogen is (1-2) × 10-9 except toward W3 D where it is ≥5 × 10-9d . The formaldehyde absorption toward the shell-like H II region W3 A is strongest toward the south/ southwest edge of the continuum source and appears to arise from a thin, compressed layer. This layer may have been compressed by the expansion of the ionized gas into part of the eastern molecular core. Publication: The Astrophysical Journal Pub Date: April 1996 DOI: 10.1086/177004 Bibcode: 1996ApJ...460..716D Keywords: ISM: H II REGIONS; ISM: ABUNDANCES; ISM: INDIVIDUAL ALPHANUMERIC: W3; ISM: MOLECULES; RADIO LINES: ISM full text sources ADS | data products SIMBAD (9)

Partitioning of crustal slip between linked, active faults in the eastern Qilian Shan, and evidence for a major seismic gap, the ‘Tianzhu gap', on the western Haiyuan Fault, Gansu (China)

SUMMARY We have studied the Cenozoic and active tectonics of the north-eastern rim of Tibet west of the Yellow River (Gansu, China) where the western Haiyuan Fault enters the eastern Qilian Shan, a high mountainous region, which was the site of the 1927 May 23, M= 8-8.3, Gulang earthquake. Fieldwork, combined with analysis of aerial photographs and satellite images, reveals consistent cumulative left-lateral offsets of postglacial geomorphic features along the fault, but no recent rupture. West of the Tianzhu pull-apart basin, the levelling of offset-terrace risers implies Holocene horizontal and vertical slip rates on the steeply south-dipping, N110E-striking fault of 11 ± 4 and 1.3 ± 0.3 mm yr-1, respectively. The presence of subordinate, mostly normal, throws due to local changes in fault strike, and kinematic compatibility at the SW corner of the Tianzhu basin, constrains the azimuth of the fault-slip vector to be N110-115E. On the less prominent, N85-100E-striking Gulang Fault, which splays eastwards from the Haiyuan Fault near 102.2°E, less detailed observations suggest that the average Holocene left-slip rate is 4.3 ± 2.1 mm yr-1 with a minor component of ˜˜N-directed thrusting, with no recent seismic break either. East of ˜˜103°E, coeval slip on both faults thus appears to account for as much as 15 ± 6 mm yr-1 of left-lateral movement between NE Tibet and the southern edge of the Ala Shan Platform, in a N105 ± 6E direction. West of ˜˜103°E structural and geomorphic evidence implies that ˜˜NNE-directed shortening of that edge across the rising, north-eastern Qilian mountain ranges occurs at a rate of 4 ± 2 mm yr-1, by movement on right-stepping thrusts that root on a 10-20°S-dipping decollement that probably branches off the Haiyuan Fault at a depth of ˜˜25 km. The existence of fresh surface breaks with metre-high free faces on a N-dipping, hanging-wall normal fault south of the easternmost, Dongqingding thrust segment, and of half-metre-high pressure ridges on that segment, indicates that the 1927 Gulang earthquake ruptured that complex thrust system. The ˜˜4 mm yr-1 shortening rate is consistent with the inference that the thrusts formed and move as a result of orthogonal slip partitioning in a large restraining bend of the Haiyuan Fault. Based on a retrodeformable structural section, we estimate the cumulative shortening on the Qilian Shan thrusts, north of the Haiyuan Fault, to be at least 25 km. The finite displacements and current slip rates on either the thrusts or the left-lateral faults imply that Cenozoic deformation started in the Late Miocene, with slip partitioning during much of the Plio-Quaternary. Assuming coeval slip at the present rates on the Haiyuan and Gulang Faults in the last 8 Ma would bring the cumulative left-lateral displacement between NE Tibet and the Ala Shan Platform to about 120 km, consistent with the 95 ± 15 km offset of the Yellow River across the Haiyuan Fault, but many times the offset (˜˜16 km) inferred on one rccent strand of that fault east of the river. Relative to the SE Gobi Desert, NE Tibet thus appears to have moved by a fair amount in the Late Cenozoic and is still moving fast. While some of this motion probably contributes to displace (towards the ESE) and rotate (CCW) the south-west edge of the Ordos block, much of it appears to be transmitted to the South China block, which leads, with the additional contribution of other large left-slip faults to the south and despite thrusting in the Lungmen Shan, to the extrusion (towards the ESE-SE) of that block relative to the Gobi, hcncc to north-eastern Asia. The ˜˜260 km long western Haiyuan Fault links two faults that ruptured about 70 years ago during two great earthquakes only seven years apart. Despite spectacular evidence of Holocene movement, it bears no trace of a large earthquake in the past eight centuries, either in the field or in the historical record. Given its relatively high slip rate, it should therefore be singled out as one of the most critical sites for impending great earthquakes (at least M ≥ 7.5, probably M ≥ 8) in the region. That such a seismic gap, called here the ‘Tianzhu gap', lies only ˜˜100 km north of Lanzhou and Xining, largest population centres of west-central China, makes instrumental monitoring of that fault particularly urgent. That the M ˜˜ 8, Gulang earthquake ruptured a complex thrust surface under high mountains in a restraining bend of the Haiyuan strike-slip fault suggests that the occurrence of comparable earthquakes in other areas with similar fault geometry, such as south of the big bend of the San Andreas Fault in California, should not be ruled out.

Resolution of prominent crustal scatterers near the Noress small-aperture array

Our goal is to identify prominent scatterers near seismic arrays so that the secondary phases they generate can be anticipated and recognized as being of local, not teleseismic, origin. Toward this end we have developed a technique to scan seismic coda recorded by arrays for phases generated locally by scattering of teleseismic energy from large topographical and crustal heterogeneities. In this paper we test the technique by using the NORESS small-aperture array in southern Norway to image free surface secondary Rg sources excited by incoming teleseismic P waves. In essence, our technique suppresses the teleseismic energy and migrates the residual array records to image-coherent local sources. To assess the azimuthal and radial resolution that the NORESS array provides we have analysed point-source synthetics. A preliminary analysis of recorded data provides an initial view of the scatterers in the vicinity of NORESS and identifies limitations of imaging using the full coda of individual events. Single events can be used to image scatterers but more robust images, with higher azimuthal resolution, can be obtained by using a broadly distributed suite of events. Radial resolution of scatterers can be enhanced by deconvolution. A composite image generated by simultaneously considering a suite of 31 deconvolved teleseisms indicates that two secondary Rg sources are present at, or near, the free surface near NORESS. One, 27 km to the south-west of the array, appears to be related to dramatic topographic relief at the south-west edge of Lake Mjosa. Another, roughly 10 km to the east of the array is judged by a bootstrap-resampling analysis to be only marginally significant. This apparent source does not coincide with obvious topography and is likely buried. Although the time delay that separates the scattered and ‘parent’ phases depends somewhat on the angle of approach of the incoming waves, in general these secondary sources are contributing wave trains to the seismic coda that begin ˜ 4 and 11s, respectively, after the primary onset.

A new Arabian stone tool assemblage and notes on the Aterian industry of North Africa

An unusual stone tool assemblage, reported for the first time in the Arabian Peninsula, occurs at the southwest edge of the Rub’al Khali desert. The assemblage is characterized by large, unifacially worked, prominently tanged points and scrapers. An age of between about 20,000 and 35,000 years B.P., when the Rub’al Khali was a well‐watered grassland, is likely. Typological affinity with the Aterian stone tool industry of North Africa is suggested. Aterian toolmakers were a vigorous population of desert hunters, ranging over much of North Africa and the Sahara during a wet phase of the late Pleistocene. Pursuit of animals running in herds may have been a hunting strategy reflected in some of the Aterian and Arabian tools. Typology of the tanged tools and the palaeogeographic context in which they occur suggest certain specific functional usage.

34S/32S Ratios of the dissolved Sulphate of River, Well and Spring Waters in a Gypsum-Carbonate Karst Area at the Southwest Edge of the Harz Mountains

34S/32S Ratios of the dissolved Sulphate of River, Well and Spring Waters in a Gypsum-Carbonate Karst Area at the Southwest Edge of the Harz Mountains