POSITION OF ARSENIC MINERALS IN THE METALLOGENIC SERIES.

The fact that there is certain definite order in the distribution of metallic ores around a central magma has now been generally recognized by economic geologists and its effects on the geographic distribution as well as     

Active wrench faults of Iran,Afghanistan and Pakistan

The fault pattern of Iran, Afghanistan, and Pakistan has been mapped from air-photo-mosaics. The Herat, Chaman, Shahrud, Doruneh, and Zagros are the five major active faults and are wrench in character. With the exception of the Chaman fault, which lies to the east, the faults or their extensions spiral out from a centre in the Dasht Lut Depression of eastern Iran, the dextral faults spiralling out clockwise and the sinistral faults anticlockwise. The spiral fault pattern is consistent with that expected from a central force, and from the relation between the sense of horizontal displacement and the direction of outspiralling it is inferred that the crustal blocks west of the Chaman fault are moving in towards the Lut Centre. Similar spiral fault patterns can be recognized at many places in the world, and their centres are probably critical for explaining present day tectonics.-- , , , . — , , , — . , , , .

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Zusammenfassung Auf einer beigegebenen Karte wird der Verlauf von aktiven und von vermutlichen Hauptverwerfungen in Afghanistan, Pakistan und im Iran gezeigt, wie er anhand von Luftbild-Mosaikkarten und Luftaufnahmen bestimmt wurde. Die fünf wichtigsten aktiven Dislokationen sind die Herat-, Chaman-, Sharud-, Doruneh- und die Zagros-Verwerfung.Die deutlich sichtbare Herat-Verwerfung erstreckt sich in ENE-Richtung über 800 km durch den Nordteil Afghanistans zur chinesischen Grenze. Ihre Verschiebung erfolgte rechtsläufig, so daß die nördliche Scholle relativ zur südlichen nach E versetzt wurde.Die etwa 700 km lange nach SSW weisende Chaman-Verwerfung zieht sich in zwei schwach gegensinnig geschwungenen Bögen von der Herat-Verwerfung wenig N Kabul die afghanisch-pakistanische Grenze entlang, um in zahlreiche Zweigverwerfungen aufzuspalten, die in Westpakistan nach W umbiegen. Die Verschiebung erfolgte linksläufig und ist gut sichtbar.Die Sharud-Verwerfung im Iran erstreckt sich nach ENE durch die Achse des Elburs-Gebirges und biegt dann nach SE parallel zur russischen Grenze ab. Die Verwerfung ändert häufig ihre Richtung und ist nur schwer zu verfolgen. Sie hat eine sichere Länge von 800 km und ist linksläufig.Die gut sichtbare Doruneh-Verwerfung verläuft in Kurven 250 km südlich der Sharud-Verwerfung derselben parallel. Nach E spaltet sie sich auf, nach W vereinigt sie sich vermutlich mit der Sharud-Verwerfung. Sie ist 600 km lang und linksläufig.Die Zagros-Verwerfung tritt auf Luftaufnahmen am wenigsten hervor, auf geologischen Karten ist sie jedoch eine Hauptverwerfung. Sie erstreckt sich vom Schnittpunkt der drei Grenzen des Iran, Irak und der Türkei 950 km nach SE bis fast zur pakistanischen Grenze, wo sie wahrscheinlich anfangs nach NW, später nach N umbiegt. Die Verwerfung ist wahrscheinlich rechtsläufig.Die fünf Hauptverwerfungen, zusammen mit vier kleineren Verwerfungen, deren horizontaler Verschiebungssinn bekannt ist, bilden ein relativ einfaches Strukturmuster.Mit Ausnahme der Chaman-Verwerfung, die im E liegt, verlaufen die Verwerfungen oder ihre Ausläufer ausgehend von einem in der Dasht Lut-Senke gelegenen Zentrum in Gestalt einzelner Spiralen sternförmig nach allen Seiten; die in ihrem Verschiebungssinn rechtsläufigen im Uhrzeigersinn gebogen, die linksläufigen in Gegenrichtung gekrümmt. Die übrigen geologischen und morphologischen Hauptlinien zeigen ebenfalls eine derartige Anordnung mit demselbenZentrum. Das damit gegebene Strukturmuster läßt die Einwirkung einer zentralen Kraft vermuten. Aus dem Zusammenhang zwischen horizontalem Verschiebungssinn und der Richtung der einzelnen Spiralen ist zu schließen, daß sich die westlich der Chaman-Verwerfung liegenden Krustenblöcke in Richtung auf das Lut-Zentrum bewegten.Derartige Verwerfungssysteme sternförmig-spiraler Anordnung scheinen kritische Punkte im heutigen tektonischen Bild der Erde zu sein, wobei das Westende der Poebene und die Banda-See zwei der auffallendsten Zentren sind. Ebenso verlaufen die pazifischen Inselbögen in Spiralen, die sich gleichfalls in solchen Zentren treffen könnten.

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Résumé Une carte des failles actives de la Perse, de l'Afghanistan, et de la Pakistan a été dressée d'après des photos-aériennes et des photos-mosaïques. Les ruptures des filets et des rivières montrent que le rejet net est presque horizontal. Cinq failles sont dextrales, et quatre sont sinistrales. Des lignes qui montrent la direction de la maximum contraction horizontale, déterminée par les failles, encerclent la Dasht Lut dépression dans la Perse orientale.

     

Was the M<Subscript>w</Subscript> 7.5 1952 Kern County,California, earthquake induced (or triggered)?

Several recent studies have presented evidence that significant induced earthquakes occurred in a number of oil-producing regions during the early and mid-twentieth century related to either production or wastewater injection. We consider whether the 21 July 1952 M_w 7.5 Kern County earthquake might have been induced by production in the Wheeler Ridge oil field. The mainshock, which was not preceded by any significant foreshocks, occurred 98 days after the initial production of oil in Eocene strata at depths reaching 3 km, within ~1 km of the White Wolf fault (WWF). Based on this spatial and temporal proximity, we explore a potential causal relationship between the earthquake and oil production. While production would have normally be expected to have reduced pore pressure, inhibiting failure on the WWF, we present an analytical model based on industry stratigraphic data and best estimates of parameters whereby an impermeable splay fault adjacent to the main WWF could plausibly have blocked direct pore pressure effects, allowing the poroelastic stress change associated with production to destabilize the WWF, promoting initial failure. This proof-of-concept model can also account for the 98-day delay between the onset of production and the earthquake. While the earthquake clearly released stored tectonic stress, any initial perturbation on or near a major fault system can trigger a larger rupture. Our proposed mechanism provides an explanation for why significant earthquakes are not commonly induced by production in proximity to major faults.     

OBSERVATIONS ON THE HINTEREIS AND VERNAGTFERNER

Abstract

Adequate water resources management at the basin level needs quality downscaling of climate change scenarios for application to impact assessment and adaptation work. This study evaluates the ability of a regional climate model (RegCM3) to simulate the present-day climate and regional water balance over the Niger River Basin (NRB). RegCM3 gives a good simulation of the NRB hydroclimatic features. The mean bias error for monthly temperature is 1.5°C, 0.3 mm d^-1 for rainfall, and 0.4 mm d^-1 for runoff. Moderate to high correlations (0.66–0.95) were found between the modelled and the observed variables. RegCM3-based water cycling indices were not statistically different from the observation. Seasonal moistening efficiency (m) ranges between 19% and 37%; 66% of the available atmospheric moisture over NRB precipitates between June and September, of which 21% originates from local evaporation. The result suggests that the moisture sink period is July to October with very high precipitation efficiency over the basin. The model reproduces the hydroclimatology of the NRB and hence is a suitable tool for further studies relating to the assessment of climate change impacts on river basin water systems.

Editor Z. W. Kundzewicz; Associate editor D. Hughes     

Mechanisms controlling the temporal variation of the sea ice edge in the Southern Ocean

This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift. Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge.     

The response of ionospheric convection in the polar cap to substorm activity

We report multi-instrument observations during an isolated substorm on 17 October 1989. The EISCAT radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71°-78°. SAMNET and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. IMP-8 magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux to the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71° by the time of the expansion phase onset. A westward electrojet, centred at 65.4°, occurred at the onset of the expansion phase. This electrojet subsequently moved poleward to a maximum of 68.1° at 2000 UT and also widened. During the expansion phase, there is evidence of bursts of plasma flow which are spatially localised at longitudes within the substorm current wedge and which occurred well poleward of the westward electrojet. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the “distant” neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase. It is not obvious whether the electrojet mapped to a near-Earth neutral line, but at its most poleward, the expanded electrojet does not reach the estimated latitude of the polar cap boundary.     

Remote Sensing of Eupatorium Adenophorum Spreng Based on HJ-A Satellite Data

In the southwest of China, one of the greatest threats to local ecosystem is the area expansion of an invasive species, i.e., Eupatorium adenophorum Spreng (EAS). In this study, the remote-sensing technology was used to detect and map the spatial distribution of EAS in Guizhou Province, China. A series of vegetation indices, including normalized difference vegetation index (NDVI), simple ratio index (SRI) and atmospherically resistant vegetation index (ARVI), were used to identify EAS from HJ-A Chninese satellite data. According to the analysis results of fieldworks from March 21 to 22, 2009, it was found that the vegetation index of {1.9589 ≤ SRI ≤ 4.1095}∩{0.2359 ≤ ARVI ≤ 0.5193} was the optimal remote-sensing parameter for identifying EAS from HJ-A data. According to the spatial distribution of EAS estimated from HJ-A data, it was found that EAS was rather more in southwest of Guizhou Province than in northeast. EAS became sparse from southwest to northeast gradually, and the central Guizhou Province was the ecological corridor linking EAS in southwest to that in northeast. By comparison with validated data collected by the government of Guizhou Province, it was found that the uncertainty of remote-sensing method was 18.52%, 29.31%, 8.77% and 9.46% in grassland, forest, farmland and others respectively, and the mean uncertainty was 13.29%. Owing to the lower height of EAS than many plants in forest, the uncertainty of EAS was the greatest in forest than that in grassland, farmland and so on.     

Smithsonian Institution’s Global Volcanism Network

Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network, vol. 31, no. 4, April 2006 (on the Internet at ). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents. The reports contain the names and contact information for all sources. Please note that these reports are preliminary and subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism, seismic unrest, monitoring data, and field observations.