On 29–30 November 2006, heavy rains from Supertyphoon Durian remobilized volcanic debris on the southern and eastern slopes
of Mount Mayon, generating major lahars that caused severe loss of life and property in downstream communities. The nearby
Legaspi City weather station recorded 495.8 mm of rainfall over 1.5 days at rates as high as 47.5 mm/h, far exceeding the
initiation threshold for Mayon lahars. For about 18 h, floods and lahars from the intense and prolonged rainfall overtopped
river bends, breaching six dikes through which they created new paths, buried downstream communities in thick, widespread
deposits, and caused most of the 1,266 fatalities. In order to mitigate damage from future lahars, the deposits were described
and analyzed for clues to their generation and impact on structures and people. Post-disaster maps were generated from raw
ASTER and SPOT images, using automated density slicing to characterize lahar deposits, flooded areas, croplands, and urbanized
areas. Fieldwork was undertaken to check the accuracy of the maps, especially at the edges of the lahar deposits, and to measure
the deposit thicknesses. The Durian event was exceptional in terms of rainfall intensity, but the dikes eventually failed
because they were designed and built according to flood specifications, not to withstand major lahars. 相似文献
In this study, the historical distribution of metals, phosphorous, and sulfur at four different depths in the sediments of different lakes formed in the course of an urban river (in Londrina, Parana State, Brazil) were determined. The transport of metals along the course of the river was observed mainly for Mn, Cr, and Zn. High concentrations of Pb in the Capivara Bay and Cr in the river were attributed to contamination from a battery plant and a tannery, respectively. The concentrations of heavy metals in the deepest layers of the sediments remain high several years after deposition. 相似文献
Abstract. Three calcareous sedimentary rock-hosted Carlin type-like gold prospects were mapped in a mineral production sharing agreement area of Philex Gold Philippines Inc. in Taganaan municipality, Surigao del Norte province in Mindanao island in the Philippines. They occur along a 20–25 km long trend of known epigenetic gold and porphyry copper deposits that lie close to several splays of the Philippine Fault Zone. The gold district forms part of the Late Cretaceous Eastern Mindanao Range that hosts early Paleogene and late Pliocene to Quaternary intrusive rocks. Gold is invisible in the jasperoid outcrops in Lascogon, Napo, and Danao prospects. The jasperoids occur in lenses of marls belonging to the Taganaan Marl Member that is associated to a turbiditic member of the Middle Miocene Mabuhay Formation. The marl lenses include gently dipping interbedded silty limestones and calcareous shales. The "invisible gold" mineralization in silicified calcareous rocks resembles Carlin-type deposits. Based on the mapped igneous and sedimentary rocks, a possible heat source for the gold mineralization is either or both of the two main phases of intrusion, Mabuhay An-desite or Alipao Andesite Porphyry. Forty-eight rock samples, fifteen stream sediment samples, and one soil sample were critical in delineating the general features of the potential Carlin-type prospects. The gold grades of jasperoids in the three prospects range from trace amounts to 20 g/t Au. Regional studies of gold and porphyry copper mineralization in the Surigao del Norte mineral district are important in delineating ore targets for drilling in the three prospects. 相似文献
The progressive electrification of the building conditioning sector in recent years has greatly contributed to reducing greenhouse gas emissions by using renewable energy sources, particularly shallow geothermal energy. This energy can be exploited through open and closed shallow geothermal systems (SGS), and their performances greatly depend on the ground/groundwater temperature, which can be affected by both natural and anthropogenic phenomena. The present study proposes an approach to characterize aquifers affected by high SGS exploitation (not simulated in this work). Characterization of the potential hydro/thermogeological natural state is necessary to understand the regional flow and heat transport, and to identify local thermal anomalies. Passive microseismic and groundwater monitoring were used to assess the shape and thermal status of the aquifer; numerical modeling in both steady-state and transient conditions allowed understanding of the flow and heat transport patterns. Two significant thermal anomalies were detected in a fluvio-glacial aquifer in southern Switzerland, one created by river water exfiltration and one of anthropogenic nature. A favorable time lag of 110 days between river and groundwater temperature and an urban hot plume produced by underground structures were observed. These thermal anomalies greatly affect the local thermal status of the aquifer and consequently the design and efficiency of current and future SGS. Results show that the correct characterization of the natural thermo-hydrogeological status of an aquifer is a fundamental basis for determining the impact of boundary conditions and to provide initial conditions required to perform reliable local thermal sustainability assessments, especially where high SGS exploitation occurs.
The modeling of UV and optical spectra emitted from the symbiotic system AG Dra, adopting collision of the winds, predicts soft X-ray bremsstrahlung from nebulae downstream of the reverse shock with velocities > 150 km s?1 and intensities comparable to those of the WD black body flux. At outbursts, the envelop of debris, which corresponds to the nebula downstream of the high velocity shocks (700–1000 km s?1) accompanying the blast wave, absorbs the black body soft X-ray flux from the WD, explains the broad component of the H and He lines, and leads to low optical-UV–X-ray continuum fluxes. The high optical-UV flux observed at the outbursts is explained by bremsstrahlung downstream of the reverse shock between the stars. The depletion of C, N, O, and Mg relative to H indicates that they are trapped into dust grains and/or into diatomic molecules, suggesting that the collision of the wind from the WD with the dusty shells, ejected from the RG with a ～1 year periodicity, leads to the U-band fluctuations during the major bursts. 相似文献
The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation. 相似文献
