Seismic activity in the snowy mountains region and its relationship to geological structures     

J. R. Cleary  H. A. Doyle  D. G. Moye 《Australian Journal of Earth Sciences》2013,60(1):89-106

Forty‐four tremors which occurred in the Snowy Mountains of New South Wales during the years 1958–1962 have been accurately located, using a network of seismic stations operating in that area. The largest of these were a tremor of magnitude 5 north of Berridale in May, 1959, and one of magnitude 4 near Rock Flat in September, 1958. Fault plane analysis suggests that the former was caused by a high‐angle thrust movement along the plane of the Crackenback Fault, while the latter may be associated with the Murrumbidgee Fault. These conclusions are supported by macroseismic data.

Twenty‐one minor shocks occurred in the vicinity of the Berridale tremor, and their strain release pattern is that of an after‐shock sequence. It is believed that they were produced as a result of secondary strains imposed by the original motion along an edge of the faulted block. The first motion data for these shocks is consistent with the hypothesis that the associated movements were transcurrent.

With the decrease of activity in the Berridale region, tremors became more or less random in the Snowy Mountains. The strain release curve obtained for these movements suggests a gradual rebuilding of the stress field following the Berridale shock.  相似文献   

Hydrologic Versus Biogeochemical Controls of Denitrification in Tidal Freshwater Wetlands     

Scott Ensign  Kaylyn Siporin  Mike Piehler  Martin Doyle  Lynn Leonard 《Estuaries and Coasts》2013,36(3):519-532

Tidal freshwater wetlands (TFW) alter nitrogen concentrations in river water, but the role of these processes on a river’s downstream nitrogen delivery is poorly understood. We examined spatial and temporal patterns in denitrification in TFW of four rivers in North Carolina, USA and evaluated the relative importance of denitrification rate and inundation on ecosystem-scale N₂ efflux. An empirical model of TFW denitrification was developed to predict N₂ efflux using a digital topographic model of the TFW, a time series of water level measurements, and a range of denitrification rates. Additionally, a magnitude-frequency analysis was performed to investigate the relative importance of storm events on decadal patterns in N₂ efflux. Spatially, inundation patterns exerted more influence on N₂ efflux than did the range of denitrification rate used. Temporal variability in N₂ efflux was greatest in the lower half of the tidal rivers (near the saline estuary) where inundation dynamics exerted more influence on N₂ efflux than denitrification rate. N₂ efflux was highest in the upper half of the rivers following storm runoff, and under these conditions variation in denitrification rate had a larger effect on N₂ efflux than variability in inundation. The frequency-magnitude analysis predicted that most N₂ efflux occurred during low flow periods when tidal dynamics, not storm events, affected TFW inundation. Tidal hydrology and riparian topography are as important as denitrification rate in calculating nitrogen loss in TFW; we present a simple empirical model that links nitrogen transport in rivers with loss due to denitrification in TFW.  相似文献   

Fortress Wytschaete: geological controls on the German frontline in Flanders, 1914–1917     

Peter Doyle  Simon Verdegem  Robin Schäfer 《Geology Today》2020,36(2):64-74

The Battle of Messines (Wytschaete Bogen) of June 1917 is hailed as a triumph of military geology, with the simultaneous explosion of some 19 mines leading to the Allied destruction of the German frontline positions. This story is well known and rightly celebrated; but less well understood and often overshadowed by this success is the story of the effectiveness of the German fortress positions. These were constructed in late 1914 in order to maintain the strategic aim of holding the Allies in the west while pressing the Russians through a series of offensives in east. In this, they were highly effective, even in the face of continuous Allied bombardment. This article seeks to redress this unbalance in our understanding, drawing on archaeological evidence and archival resources to present a clearer picture of the nature of the German positions.  相似文献   

Application of 4D-Variational data assimilation to the California Current System     

G. Broquet  C.A. Edwards  A.M. Moore  B.S. Powell  M. Veneziani  J.D. Doyle 《Dynamics of Atmospheres and Oceans》2009,48(1-3):69

The Incremental Strong constraint 4D-Variational (IS4DVAR) data assimilation system of the Regional Ocean Model System (ROMS) is used to study the controllability of a realistic, high resolution configuration of the California Current System. The configuration and results of assimilating both satellite-derived surface observations along with in situ data are presented. Results show consequent improvements in many characteristics of the model circulation, and some of the strengths of the adjoint method for data assimilation are highlighted. General issues of the sensitivity of the results to the configuration of ROMS-IS4DVAR are also discussed.  相似文献   

Investigation of a Complex Nocturnal Flow in Owens Valley,California Using Coherent Doppler Lidar     

Aditya Choukulkar  Ronald Calhoun  Brian Billings  James Doyle 《Boundary-Layer Meteorology》2012,144(3):359-378

A study of an interesting meteorological episode over the Owens Valley, California, USA during the Terrain-Induced Rotor EXperiment was conducted using a recently adapted statistical interpolation method to retrieve wind-velocity vectors from Doppler lidar data. This vector retrieval method has been adapted from radar data assimilation techniques. Results show that the method allows better preservation of local variations in the flow field than other techniques. In addition, a high resolution Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS^®) run is used to understand the large-scale flow within the valley and compared with lidar retrievals. Observations from 1030 UTC to 1230 UTC (0230 local time to 0430 local time) on March 27, 2006 are presented. Lidar observations show complex and uncharacteristic flows such as sudden bursts of westerly cross-valley wind mixing with the dominant up-valley wind. Model results from COAMPS and other in-situ instrumentation are used to corroborate and complement these observations. The optimal interpolation technique for Doppler lidar data vector retrieval appears well suited for scenarios with complex spatial variations in the flow field.  相似文献   

An emission measure analysis of two sunspots observed by the UVSP instrument on the SMM spacecraft     

A. E. Kingston  J. G. Doyle  P. L. Dufton  J. B. Gurman 《Solar physics》1982,81(1):47-58

The EUV observations from the SMM satellite of two sunspots are presented here. These observations show the sunspots (a) to be regions of lower intensity than the surrounding plage, contrary to that found by previous authors, and (b) to have line intensities which vary little over a period of several hours. An upper limit to mass flows of 2km s^-1 is derived, indicating a relatively simple energy balance for the chromosphere-corona transition zone with thermal conduction being balanced by radiative losses. Electron densities derived from Niv to Civ line ratios imply electron pressures (log N _eT_e) of 15.0 to 15.3.  相似文献   

Nonhydrostatic,mesobeta-scale,real-data simulations with the Penn State University/National Center for Atmospheric Research mesoscale model     

T. T. Warner  Y. -H. Kuo  J. D. Doyle  J. Dudhia  J. Dudhia  D. R. Stauffer  N. L. Seaman 《Meteorology and Atmospheric Physics》1992,49(1-4):209-227

Summary The Penn State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model is a widely used research tool that has been applied in a wide variety of real-data, mesoalpha-scale applications. Recently a nonhydrostatic version of this model has been developed by Dudhia (1993). It is the purpose of this paper to illustrate the capabilities of this modeling system by describing four examples of mesobeta-scale simulations: two of the cases involve maritime processes and two deal with continental weather events. All utilize fully three-dimensional sets of initial conditions that are based on real data, both standard data and from special measurements programs. One case employs the model in a data-assimilation configuration, wherein Newtonian relaxation terms are used in the equations to assimilate data from a variety of platforms. This example of nonhydrostatic four-dimensional data assimilation (FDDA) is performed for the purpose of generating a dynamically consistent four-dimensional data-set, however the same procedure can be used for model initialization. The first case, described in section 2, involves the simulation of a coastal front that forms offshore near the western edge of the Gulf Stream. In the second case, described in section 3, the model is used in the FDDA mode to define the mesobeta-scale windfield over the complex terrain of the region around Grand Canyon, Arizona. In sections 4 and 5 will be described the mesobeta-scale structure of cold fronts, one within a marine cyclone, and another near the Rocky Mountains.With 21 FiguresNCAR is sponsored by the National Science Foundation.  相似文献   

The effects of crack anisotropy on the hypocentral locations of local earthquakes     

Mark Doyle  Robert McGonigle  Stuart Crampin 《Geophysical Journal International》1982,69(1):137-157

Summary. Exact modelling of the earthquake location process in regions of dilatancy-anisotropy shows that failure to take account of the velocity anisotropy in the determination of local hypocentres can result in erroneous and misleading locations. In particular, the locations can indicate spurious migrations of foci from the true epicentral positions and the true depths of foci. These spurious locations may indicate planes of hypocentres deviating from the true fault plane. Observations of such phenomena have been noted several times in the literature. However, once the anisotropic model is known, a simple location program, incorporating the anisotropic velocity-variations, permits accurate location of local earthquakes using P and first S -wave arrival times.  相似文献   

Melt inclusions from the deep Slave lithosphere: implications for the origin and evolution of mantle-derived carbonatite and kimberlite   总被引：1，自引：0，他引：1  

Esm van Achterbergh  William L. Griffin  Chris G. Ryan  Suzanne Y. O'Reilly  Norman J. Pearson  Kevin Kivi  Buddy J. Doyle 《Lithos》2004,76(1-4):461-474

Melt inclusions in clinopyroxenes from lherzolitic xenoliths from the deep lithospheric mantle beneath the Slave Craton (Lac de Gras area, Canada) reveal multiple origins for carbonatitic melts. One type of inclusions consists of a series of silicate–carbonate–silicate concentric layers, interpreted to have unmixed under disequilibrium conditions during rapid ascent to the surface. Bulk major- and trace-element compositions are typical of Group 1 kimberlites and quantitative nuclear microprobe imaging of the globules reveals fractionation of related elements (e.g. F–Br, Nb–Ta) between the silicate and carbonate components. The globules probably formed by partial melting of carbonated peridotite, consistent with results of melting experiments and some models for the generation of kimberlite magmas. They provide evidence for a genetic relationship between some carbonate-rich magmas and ultramafic silicate magmas, and for the possibility of unmixing processes of these melts during their evolution.

The second inclusion type comprises carbonate-rich globules interpreted as samples of Mg-carbonatite melt that quenched on ascent to the surface. Bulk major- and trace-element compositions indicate that the melts were derived from a carbonate-rich source and oxygen, carbon, and strontium isotope data are consistent with the involvement of recycled crustal material and suggest that some mantle-derived carbonatites are unrelated to kimberlites.  相似文献   

River Channel Management: Towards Sustainable Catchment Hydrosystems     

Martin W. Doyle   《Geomorphology》2006,74(1-4):322-323

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