Das Pamir-System

Ohne Zusammenfassung     

PHOENIX-2: A New Broadband Spectrometer for Deci- metric and Microwave Radio Bursts – First Results

A broadband radio spectrometer has been put into operation at Bleien, Switzerland, to register the flare emission of the full Sun. In the frequency range of operation, 0.1 to 4.0 GHz, both modes of circular polarization are recorded continuously. The new system, Phoenix-2, has been developed from the experience with the previous Phoenix spectrometer. Improved, computer-controlled focal hardware allows now a complete daily calibration, a more sophisticated calibration procedure, and monitoring of all essential instrumental and environmental parameters. Calibrated data are now usually available the day after observation and are accessible through the Internet. The scientific improvements include a larger frequency range of observation, a larger number of completely recorded events due to full-day registration, more accurate measurements, particularly in circular polarization, and more reliable operation. First observations are presented and quantitative results comparing the calibration with single frequency instruments are reported. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005194314845     

Crooked line, rough topography: advancing towards the correct seismic image

Seismic exploration in mountainous areas imposes serious compromises on both acquisition and processing. Access restrictions usually result in profiles that are not straight and are not recorded along the true dip direction (if there is a true dip direction!). Processing constraints often result in very poor approximate corrections for elevations and for deviations from a straight line. Most fundamentally, 2D acquisition and processing assumes that the earth is 2D; this assumption is often seriously violated in mountainous areas. While we cannot efficiently correct 2D seismic data for the effects of a fully 3D subsurface, we can improve the data quality in thrust areas where the assumption of 2D subsurface variation is reasonable. We do this in a series of small steps, which improves the accuracy of several approximations made in processing 2D land data.     

Trace metals and radionuclides reveal sediment sources and accumulation rates in Jordan Cove, Connecticut

Many small estuaries are influenced by flow restrictions resulting from transportation rights-of-way and other causes. The biogeochemical functioning and history of such systems can be evaluated through study of their sediments. Ten long and six short cores were collected from the length of Jordan Cove, Connecticut, a Long Island Sound subestuary, and analyzed for stratigraphy, radionuclides (¹⁴C, ²¹⁰Pb, ²²⁶Ra, ¹³⁷Cs, and ⁶⁰Co), and metals (Ag, Cd, Cu, Pb, Zn, Fe, and Al). For at least 3,800 yr, rising sea level has gradually inundated Jordan Cove, filling it with mud similar to that currently being deposited there. Long-term sediment accumulation in the cove averaged close to 0.1 cm yr⁻¹ over the last three millennia. Recent sediment accumulation rates decrease inland from 0.84 cm yr⁻¹ to 0.40 cm yr⁻¹, and are slightly faster than relative sea-level rise at this site (0.3 cm yr⁻¹). Similarity of depth distributions of trace metals was used to confirm relative sediment accumulation rates. ⁶⁰Co and Ag are derived from sources outside the cove and its watershed, presumably the Millstone nuclear power plant and regional contaminated sediments, respectively. The combined data suggest that Long Island Sound is an important source of sediment to the cove; a minor part of total sediment is supplied from the local watershed. Trace metal levels are strongly correlated with Fe but not with either organic matter or Al. Sediment quality has declined in the cove over the past 60 yr, but only slightly. Cu, Pb, and Zn data correlate strongly with Fe but not with either organic matter or aluminum. Ratios of Ag to Fe and to trace metals suggest that Ag in the cove is derived almost entirely from Long Island Sound. This result supports the notion that Fenormalized Ag can serve as a better tracer of some kinds of contamination than more common and abundant metals, like Cu, Pb, and Zn. *** DIRECT SUPPORT *** A01BY085 00008     

Calibration of a Land Subsidence Model Using InSAR Data via the Ensemble Kalman Filter

The application of interferometric synthetic aperture radar (InSAR) has been increasingly used to improve capabilities to model land subsidence in hydrogeologic studies. A number of investigations over the last decade show how spatially detailed time‐lapse images of ground displacements could be utilized to advance our understanding for better predictions. In this work, we use simulated land subsidences as observed measurements, mimicking InSAR data to inversely infer inelastic specific storage in a stochastic framework. The inelastic specific storage is assumed as a random variable and modeled using a geostatistical method such that the detailed variations in space could be represented and also that the uncertainties of both characterization of specific storage and prediction of land subsidence can be assessed. The ensemble Kalman filter (EnKF), a real‐time data assimilation algorithm, is used to inversely calibrate a land subsidence model by matching simulated subsidences with InSAR data. The performance of the EnKF is demonstrated in a synthetic example in which simulated surface deformations using a reference field are assumed as InSAR data for inverse modeling. The results indicate: (1) the EnKF can be used successfully to calibrate a land subsidence model with InSAR data; the estimation of inelastic specific storage is improved, and uncertainty of prediction is reduced, when all the data are accounted for; and (2) if the same ensemble is used to estimate Kalman gain, the analysis errors could cause filter divergence; thus, it is essential to include localization in the EnKF for InSAR data assimilation.     

Reconstruction of fluvio-lacustrine landscapes and settlement history in the Texcoco region,Mexico, using a modern geomorphic analog

Located in the Basin of Mexico, the eastern shore of former Lake Texcoco sustained a variety of human occupations throughout the Holocene, including preceramic hunter-gatherers, incipient agriculturalists, and a variety of settlements in the ceramic periods. Nonetheless, the environmental dynamics of occupations on the lakeshore have not been fully addressed. The Archaic preagricultural Texcoco Man site (>5000 B.C.E.) and the Late Formative TX-LF-14 site (c. 550-200 B.C.E.), among others, occupy this fluvio-lacustrine transitional environment. Few stratigraphic works in and around the sites have been performed. Consequently, it is difficult to understand the dynamics of the sedimentary system in space and time. This work highlights and describes the fluvio-lacustrine sedimentary dynamics and the resulting landscape that past societies inhabited on the eastern shore of Texcoco Lake. Because the study area has been altered by historic and modern draining, our work employs Lake Santiaguillo and its main tributary, the Tejamen River in the Durango state, as a modern analog to study their sedimentary dynamics. The analyses of surface geomorphology in the Texcoco study area were employed to corroborate the modern analog interpretation. To achieve these goals, we conducted a GIS-based morphometric analysis and LANDSAT-8 imagery to study the variations in landforms through wet and dry events. The results indicate an increase in the lake volume, low bifurcation in the active fluvial channels, few inundated surfaces, and the presence of bird-foot deltaic channels during high precipitation events. In contrast, low precipitation events are characterized by reduced lake volume, increased fluvial channel bifurcation, and expanded floodplains. This heterogeneous landscape thus provided a rich source of diverse natural resources of saline and freshwater aquatic habitats. Simultaneously, constant or recurring flooding events generated a challenging landscape for prehistoric settlers who implemented diverse technologies, such as the construction of tlateles, on the levees of deltaic channels to reduce the risk and impact of flooding events.     

MicroRaman spectroscopy of anomalous planar microstructures in quartz from Mt. Oikeyama: Discovery of a probable impact crater in Japan

Abstract– Planar deformation features (PDFs) and planar fractures (PFs) have been found and confirmed by optical microscope observations and microRaman spectroscopy in quartz grains from Mt. Oikeyama (Akaishi Mountains, Central Japan), for which the semicircular topographic feature of the ridge suggests a crater formed by an impact event. According to the optical microscope observations, a low shock pressure (8–10 GPa) is estimated by the occurrence of basal or ω PDFs leading to lack of multiple sets of PDFs. In addition, a new type of planar microstructure was found in several quartz grains. The microRaman characteristics of PDFs in quartz from Mt. Oikeyama show the amorphous state indicating the presence of weak broad bands at 400 and 800 cm^?1 peak positions. These characteristics are indicative of PDFs that are limited to shocked quartz. This indicates an impact origin for distinct planar microstructures in quartz from Mt. Oikeyama.