Combination of Precise Leveling and InSAR Data to Constrain Source Parameters of the Mw = 6.5, 26 December 2003 Bam Earthquake

We used new precise leveling data acquired 40 days after the Bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 Bam earthquake. We invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture. The best-fitting dislocation model is a steeply east-dipping right-lateral strike-slip fault that has a size of 11 by 8 km and strikes N2°W. We find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake. Our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep. The slip magnitude and depth of faulting taper to the north, where the fault approaches the Bam city. Inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4%.     

Contributions to the Deformation Analysis in Germany Based on Precise and Continuous GPS Measurements

Modern space geodetic techniques enable deformation monitoring of continental plate interiors with high spatial and temporal coverage. Resolving data and results are currently evaluated for their application for the integrated assessment of seismic hazard and risk in Germany. This goes especially for regions where earthquakes are generally rare but high magnitudes are still not unrealistic while vulnerability of today’s society is steadily growing. The present contribution deals with the continuous monitoring of tectonic fracture systems in Germany using the GPS. The estimation of the station velocities with GPS and the resulting geodetic strain is supposed to provide additional input to the earthquake hazard assessment. Unfortunately, the low expected and currently seen velocities (<1–2 mm/year) make it extremely difficult to distinguish between noise and a tectonic signal. Because of the short observation interval the velocity uncertainties are about 2 mm/year in the horizontal components. The essential goal of this program is to provide and model highly precise deformation data and to discuss its needs for a better assessment of geological hazard, especially for the most active tectonic regions in Germany, the Rhine-Graben, the Swabian Alb, the Alpine foreland, and the Vogtland. Here we present preliminary results from 2 years of measurements at currently 150 GPS stations throughout Germany. The time span of this program has proven to be too short and the density of the station network to be not dense enough yet for reliable significant horizontal station velocities and supporting the earthquake hazard assessment.     

A comparison of photolysis rate parameters estimated from measured and simulated actinic flux for wintertime conditions at Storm Peak Laboratory,Colorado

Photolysis rate parameters depend upon solar actinic flux and chemical species dependent quantum yields and cross sections. Spectrally resolved measurements of actinic flux should be preferred over flux derived from models for the analysis of field observations. Actinic flux can be difficult to derive from the irradiance measurements of flat-plate radiometers. It is also difficult to estimate from models due to uncertainties in the ozone column, aerosol concentrations and distributions, cloud cover, optical depth and surface albedo. A series of actinic flux measurements were performed at Storm Peak Laboratory (3,210 m above sea level), Colorado, United States with spectroradiometers during the wintertime (January 07–10, 2004). The site is relatively remote with a clean atmosphere and during the wintertime the ground is generally covered by fresh snow with a high albedo. The actinic flux measurements were used to estimate the photolysis rate parameters of ozone, nitrogen dioxide and formaldehyde. The measured actinic flux and the photolysis rate parameters derived from the flux were compared to calculations using the Tropospheric Ultraviolet-Visible Model (TUV), version 4.2 (Madronich and Flocke, 1998). The TUV modeled actinic flux, the measured flux and the photolysis rate parameters derived from them had similar temporal patterns. However there were significant differences in their magnitude due to uncertainties in the data available to initialize the TUV model and the calibration of the spectroradiometer.     

Field study of the potential for winter precipitation enhancement in the Australian Snowy Mountains

A research program was initiated in 1988 to investigate the potential for winter snowpack enhancement in the Snowy Mountains of Australia. Field studies were conducted during the austral winters of 1988 and 1989 in order to characterize the water and ice composition of clouds passing over these mountains. We utilized a dual-channel microwave radiometer and a Ka-band (8.6 mm wavelength) radar in a coordinated observational program to document the distribution of supercooled liquid water, ice phase precipitation and water vapor in the winter storm systems. The vertical temperature, humidity and wind profiles were obtained at high temporal resolution from local rawinsonde launches. Ground-based sampling of the snow crystal types and the stable isotopic composition of the snow provided information on the processes of crystal formation and riming during these storms. A precipitation trajectory model was used to simulate ice crystal growth for snow which precipitates within the study region. Analysis of these data indicate buildup of supercooled liquid water during certain storm periods, while during other periods the ice crystal growth processes efficiently remove cloud liquid. Several aspects of the cloud seeding potential are discussed in this paper and the overall conclusion is that winter precipitation enhancement is scientifically feasible, based upon the World Meteorological Organization criterion of supercooled liquid water availability.     

Mixing of rhyolite,trachyte and basalt magma erupted from a vertically and laterally zoned reservoir,composite flow P1, Gran Canaria

The 14.1 Ma composite welded ignimbrite P1 (45 km³ DRE) on Gran Canaria is compositionally zoned from a felsic lower part to a basaltic top. It is composed of four component magmas mixed in vertically varying proportions: (1) Na-rhyolite (10 km³) zoned from crystal-poor to highly phyric; (2) a continuously zoned, evolved trachyte to sodic trachyandesite magma group (6 km³); (3) a minor fraction of Na-poor trachyandesite (<1 km³); and (4) nearly aphyric basalt (26 km³) zoned from 4.3 to 5.2 wt% MgO. We distinguish three sites and phases of mixing: (a) Mutual mineral inclusions show that mixing between trachytic and rhyolitic magmas occurred during early stages of their intratelluric crystallization, providing evidence for long-term residence in a common reservoir prior to eruption. This first phase of mixing was retarded by increasing viscosity of the rhyolite magma upon massive anorthoclase precipitation and accumulation. (b) All component magmas probably erupted through a ring-fissure from a common upper-crustal reservoir into which the basalt intruded during eruption. The second phase of mixing occurred during simultaneous withdrawal of magmas from the chamber and ascent through the conduit. The overall withdrawal and mixing pattern evolved in response to pre-eruptive chamber zonation and density and viscosity relationships among the magmas. Minor sectorial variations around the caldera reflect both varying configurations at the conduit entrance and unsteady discharge. (c) During each eruptive pulse, fragmentation and particulate transport in the vent and as pyroclastic flows caused additional mixing by reducing the length scale of heterogeneities. Based on considerations of magma density changes during crystallization, magma temperature constraints, and the pattern of withdrawal during eruption, we propose that eruption tapped the P1 magma chamber during a transient state of concentric zonation, which had resulted from destruction of a formerly layered zonation in order to maintain gravitational equilibrium. Our model of magma chamber zonation at the time of eruption envisages a basal high-density Na-poor trachyandesite layer that was overlain by a central mass of highly phyric rhyolite magma mantled by a sheath of vertically zoned trachyte-trachyandesite magma along the chamber walls. A conventional model of vertically stacked horizontal layers cannot account for the deduced density relationships nor for the withdrawal pattern.     

The major Baltic inflow in January 1993 — Measurements and modelling results

Summary Major Baltic inflows (from the Kattegat) represent the only possibility for deep water renewal in the Baltic Sea that is generally characterised by stable stratification. Such an inflow occurred in January 1993 for the first time in 16 years. Observations were made by a moored station at Darß Sill and, for the first time since investigations into major Baltic inflows began, by a research vessel. In addition, the event has been simulated in an operational model.

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Der Salzwassereinbruch vom Januar 1993 in die Ostsee-Messungen und Modellergebnisse

Zusammenfassung Für die im allgemeinen stabil geschichtete Ostsee bilden Salzwassereinbrüche (aus dem Kattegat) die einzige Möglichkeit zur Erneuerung des Tiefenwassers. Ein solcher Salzwassereinbruch ereignete sich nach 16 Jahren Unterbrechung erst wieder im Januar 1993. Dieser Vorgang wurde durch Messungen von einer permanenten Station auf der Darßer Schwelle und — erstmals in der Geschichte der Erforschung von Salzwassereinbrüchen —einem Forschungsschiff registriert. Außerdem liegt eine numerische Simulation mit einem operationellen Modell vor.

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Insertion d'eau salée dans la mer Baltique en janvier 1993. Mesures et exploitation d'un modèle numérique

Résumé L'apport d'eau salée en provenance du Kattegat reste la seule possibilité de renouvellement des eaux profondes des couches stables de la mer Baltique. Un telle insertion d'eau salée ne s'est produite qu'au mois de janvier 1993 après une interruption de 16 ans. Ce processus a été enregistré par des mesures d'une station permanente (Darßer Schwelle) et, pour la première fois dans l'histoire de l'étude des insertions d'eau salée, par un navire scientifique. En outre une simulation numérique à l'aide d'un modèle opérationnel est présentée.

     

Flow directions in Columbia River Basalt flows and paleocurrents of interbedded sedimentary rocks,South-Central Washington

More than 150 flow directions measured mainly in inclined pipe vesicles and, more rarely, vesicle cylinders, spiracles, and inclined foreset beds in pillowpalagonits-complexes) of the upper 12 widespread Yakima Basalt flows on the Columbia River Plateau in south-central Washington indicate rather uniform transport directions from southeast to northwest. This strongly supports former ideas that the large Grande Ronde-Cornucopia dike swarm in northeast Oregon fed the huge lava floods. It is shown that all previous evidence indicating eruption centers for the basalts in the Cascada Range to the west is inconclusive. Cross-bedding directions, maximum pebble sizes, and distribution of heavy mineral suites in sedimentary deposits interbedded with the basalt sheets delineate in more detail two main paleoslopes whose deposits interfinger:

1. a)
   the Cascade paleoslope to the west with east-southeast paleocurrents and a predominance of volcanic heavy minerals (hornblende, oxyhornblende, hypersthene, and clinopyroxene).