Duration Magnitude Scale and Site Residuals for Northern Morocco     

Issam Mouayn  Ben Aissa Tadili  Lahsen Aït Brahim  Mohamed Ramdani  Mohamed Limouri  Nacer Jabour 《Pure and Applied Geophysics》2004,161(5-6):1061-1080

— The first empirical duration magnitude (M_D) formula is developed and tested for the Northern Morocco Seismic Network (NMSNET). This relationship is obtained by relating the IGN (Instituto Geografico National, Madrid) body-waves mbLg^IGN to the duration (), and the epicentral distance (), at 25 analogue stations of the NMSNET for 479 earthquakes with 2.5 mb 5.4, from March 1992 to February 2001. M_D estimates are significantly more precise while introducing a correction term for each of these stations, cSta_j. The magnitude for the i^th event (M_D)_i is the mean value of individual M_Dij=–0.14+1.63log₁₀(_ij)+0.031(_ij)+cSta_j. The cSta_j corrections reduce considerably the local site effects which influence the recorded durations and cause stations to either overestimate, or underestimate M_D up to 0.5 magnitude units. Average station M_D residuals (–cSta_j) are found to be independent of the distance from the epicenter to at least 10 degrees. It seems evident that regional geological features in the immediate behavior of stations have a systematic effect on the corresponding obtained residuals: older well-consolidated Precambrian crystalline rocks produce high negative residuals (shorter durations), younger unconsolidated sediments produce high positive residuals (longer durations), whereas, intermediate M_D site residuals appear to be the result of the effect of various factors, principally age and state of consolidation of the bedrock, combined with the local tectonic.  相似文献   

The late thermal history of the Ronda area, southern Spain     

Jos Julin Esteban  Lourdes Snchez-Rodríguez  Diane Seward  Julia Cuevas  Jos María Tubía 《Tectonophysics》2004,389(1-2):81-92

The Betic–Rif belt, in the western Mediterranean, experienced a pre-Alpine history and was later extensively reworked by major Alpine tectonics. There is abundant data showing that the Betic chain suffered very high cooling rates during its Alpine history, constrained mainly by geochronology using various isotopic systems and by palaeontological age determinations. In the westernmost part of the chain the high closure-temperature isotopic systems recorded Miocene high-grade metamorphism in the country rocks. In order to constrain the later stages of cooling, fission-track analysis has been applied to both zircon and apatite. The results point to extremely high rates of cooling (400 °C/Ma) between 21 and 19 Ma. Rates slowed to 100 °C/Ma for the time period 19 to about 12 Ma. The fission-track analysis also confirms the existence of an extensional tectonic stage between 19 and 17 Ma.  相似文献   

Material referred to Megalosaurus (Dinosauria: Theropoda) from the Middle Jurassic of Stonesfield, Oxfordshire, England: one taxon or two?     

Julia J. Day 《Proceedings of the Geologists' Association. Geologists' Association》2004,115(4):359-366

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Observations of Solitary Waves in the Stable Atmospheric Boundary Layer     

Julia M. Rees  Philip S. Anderson  John C. King 《Boundary-Layer Meteorology》1998,86(1):47-61

Large amplitude, isolated, wave-like phenomena have been observed in the lowest 40 m of the strongly stably stratified atmospheric boundary layer overlying a coastal Antarctic ice shelf. The waves only occur when prevailing wind speeds are low. They always propagate from over the land, with phase speeds exceeding the local mean wind speed. They have wavelengths of the order of 200 m. Several examples are described and a summary of the statistical properties of these waves events is presented.  相似文献   

Observation of converted Moho reflections in the north-west of the Iberian Peninsula     

Julia Téllez  Diego Córdoba 《Geophysical Journal International》1996,124(1):7-17

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Heat flow and regional uplift at the north-eastern border of the Ebro basin, NE Spain     

Julia Cabal  Manel Fernàndez 《Geophysical Journal International》1995,121(2):393-403

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Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the water framework directive   总被引：9，自引：0，他引：9  

Jochen Schaumburg  Christine Schranz  Julia Foerster  Antje Gutowski  Gabriele Hofmann  Petra Meilinger  Susanne Schneider  Ursula Schmedtje 《Limnologica》2004,34(4):283-301

A new assessment system for macrophytes and phytobenthos in German rivers meeting the requirements of the Water Framework Directive (WFD) of the European Community is described. Biocoenotic types based on biological, chemical and hydromorphological data from over 200 river sites covering the main ecoregions, hydromorphological stream types and degradation forms have been defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into three components: macrophytes, benthic diatoms and remaining phytobenthos. For macrophytes seven types including one subtype, for benthic diatoms 14 types including three subtypes and for the remaining phytobenthos five river types were identified. The benthic vegetation at reference condition was described for most of the river types. Degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For some of the described river types additional investigations are necessary before a classification system can be developed.  相似文献   

The Pacific Northwest Coastal Ecosystems Regional Study     

Julia K. Parrish  Robert Bailey  Andrea E. Copping  John E. Stein 《Estuaries and Coasts》2003,26(4):991-993

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Seabirds as indicators: An exploratory analysis of physical forcing in the Pacific Northwest coastal environment     

Julia K. Parrish  Stephani G. Zador 《Estuaries and Coasts》2003,26(4):1044-1057

Bottom-up control, or physical forcing of upper trophic populations, is often cited as a major factor regulating marine species. In particular, seabirds are often cited as indicators of relative productivity and health of the marine environment. The degree to which physical forcing plays a dominant role and the mechanisms of effect remain unclear. We test the relationship between measures of oceanographic and atmospheric forcing, proxied by commonly available monthly to daily indices, and the response of populations of a ubiquitous seabird of the Pacific Northwest coastal environment, the common murre,Uria aalge. We constructed two models: an annualized bottom-up model that examines the degree to which population response variables, including population size, breeding success, and foraging parameters, are correlated with oceanographic forcing at space and time scales relevant to murre biology; and a daily direct forcing model that examines the degree to which diet choices reflect specific, local oceanographic signals. Our bottom-up model suggests that murres are regulated by bottom-up forcing, and that the strength of the association between physical change and population response may be mediated by density dependence. Our direct forcing model indicated that chick diet is affected by both local and remote parameters, including upwelling, tide, and the Pacific Decadal Oscillation. We conclude that murres, and seabirds in general, can be used as indicators of local to basinwide physical change, but only under certain conditions: the life history of the species, and the specific local population, must be well known; a conceptual model that links life history traits to measures of physical change at biologically relevant space and time scales must be developed; and larger populations that are more apt to show density-dependent effects should be selected.  相似文献   

The use of large bottomless lysimeters in the determination of water balances for a raised mire     

Julia C. Kelemen  Hugh A. P. Ingram 《水文研究》1999,13(1):101-111

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