Meteorological noise in crustal gas emission and relevance to geochemical exploration     

Ronald W. Klusman  James D. Webster 《Journal of Geochemical Exploration》1981,15(1-3)

The emission of gas from the earth's crust is a complex process influenced by meteorological and seasonal processes which must be understood for effective application of gas emission to geochemical exploration. Free mercury vapor emission and radon emanation are being measured in a shallow instrument vault at a single nonmineralized site in order to evaluate these influences on gas emission.Mercury concentrations in the instrument vault average 9.5 ng/m³ and range from < 1 ng/m³ to 53 ng/m³ with a strong seasonal effect. Mercury has a direct relationship to vault temperature, air temperature, soil temperature, barometric pressure, water table, and the frozen or thawed state of the soil. Air and soil temperature, barometric pressure, and relative humidity are most important in influencing mercury emission while soil moisture is also important in radon emanation. Diurnal cycles are common but do not occur on all days. A heavy precipitation event on a dry soil seals the soil resulting in a rise in mercury concentration. Precipitation on a soil that is already wet does not increase mercury emission because of the compensation caused by lowering of the soil temperature by the precipitation event. Freezing of the soil changes the physical state of the vault-soil-soil gas-atmosphere system and emits the lowest concentrations of mercury. Phase lag effects are likely important. Stepwise multiple regression of mercury as dependent variable with meteorological and seasonal parameters as independent variables gives a cumulative R value of 0.563 and R² of 0.317. The short-term noise coupled with phase lags are an important factor.The radon measurements integrated over weekly intervals smooth out much of the short-term noise. Stepwise multiple regression of radon as dependent variable with meteorological and seasonal parameters as independent variables gives a cumulative R value of 0.967 and R² of 0.934. In this portion of the study the variation in the radon emanation is adequately predicted by meteorological and seasonal parameters.  相似文献   

Magnetic effects associated with chemical changes in igneous rocks     

Ronald T. Merrill 《Surveys in Geophysics》1975,2(3):277-311

Experimental evidence and theory indicate that chemical changes occur in many igneous rocks at sufficiently low temperatures to significantly affect the remanent magnetization. Some chemical changes lead to self-reversals of magnetization that are not reproducible in laboratory experiments. Such self-reversals appear to be very rare in subaerially-erupted basalts, but they probably are much more common in some other rock types, such as granites and diorites. The stability of the natural remanent magnetization in igneous rocks can be decreased, left unaltered, or increased by chemical changes. In addition, chemical changes will usually affect the intensity of magnetization in a rock; the intensity can increase, decrease, or (rarely) be left unaltered by a chemical change. Such changes are important to consider in the development of improved techniques for obtaining reliable estimates of the intensity of the Earth's magnetic field in the past and in correctly interpreting marine magnetic anomalies. Finally, experiments and theory are presented which suggest that many of the chemical changes in igneous rocks will only occasionally produce significant changes in the direction of the magnetization.  相似文献   

REPLY TO the preceding Discussion by Ronald W. Crites and Sherwood C. Reed of "Land Application of Waste – An Accident Waiting to Happen"     

Ronald W. Crites  Sherwood C. Reed 《Ground water》1979,17(6):608-608

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Transmission of tidal energy over a plateau   总被引：1，自引：0，他引：1  

Ronald Allan Heath 《Ocean Dynamics》1979,32(6):289-296

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Gypsum and halite from the Mid-Atlantic Ridge,DSDP Site 395     

James I. Drever  James R. Lawrence  Ronald C. Antweiler 《Earth and Planetary Science Letters》1979,42(1):98-102

Gypsum and halite crystals, together with saponite and phillipsite, were found in a vein in a basalt sill 625 m below the sea floor at DSDP Site 395A, located 190 km west of the crest of the Mid-Atlantic Ridge. The δ³⁴S value of the gypsum (+19.4‰) indicates a seawater source for the sulfate. The δ¹⁸O values of the saponite (+19.9‰) and phillipsite (+18.1‰) indicate either formation from normal seawater at about 55°C or formation from¹⁸O-depleted seawater at a lower temperature.The gypsum (which could be secondary after anhydrite) was formed by reaction between Ca²⁺ released from basalt and SO₄^2? in circulating seawater. The halite could have formed when water was consumed by hydration of basalt under conditions of extremely restricted circulation. A more probable mechanism is that the gypsum was originally precipitated as anhydrite at temperatures above 60°C. As the temperature dropped the anhydrite converted to gypsum. The conversion would consume water, which could cause halite precipitation, and would cause an increase in the volume of solids, which would plug the vein and prevent subsequent dissolution of the halite.  相似文献   

A comparison of ARM and TRM in magnetite     

Shaul Levi  Ronald T. Merrill 《Earth and Planetary Science Letters》1976,32(2):171-184

Experiments comparing anhysteretic remanence (ARM) and thermoremanence (TRM) in samples containing natural and synthetic magnetite, whose mean particle sizes range from single domain to multidomain, show that ARM and TRM are very similar (but not identical) in their stabilities with respect to alternating field (AF) demagnetization, temperature cycles in zero field to below magnetite's isotropic temperature near 130°K, and stability with respect to spontaneous decay in zero field. Therefore, for magnetites, ARM can be used to model (with reasonable success) these stability properties of TRM. The field dependence of the acquisition of ARM and TRM shows that the low field susceptibility ratio, χ_ARM/χ_TRM, has a particle size dependence, increasing from 0.1 for certain submicron particles to 2.0 for large multidomain crystals. Even for samples whose remanence is predominantly carried by submicron particles χ_ARM/χ_TRM is highly variable, 0.11 ≤ χ_ARM/χ_TRM ≤ 0.50. Therefore, ARM paleointensity methods which do not take into account the large variability in and the particle size dependence of χ_ARM/χ_TRM are subject to order-of-magnitude uncertainties.  相似文献   

The essex earthquake of 1884     

Ronald F. Scott 《地震工程与结构动力学》1977,5(2):145-155

The largest British earthquake to occur in several hundred years took place in Essex, in the south east of England, in 1884. From contemporary accounts and a recent visit to the area affected by the earthquake, the intensity of the earthquake was assessed. It is estimated that the peak accelerations generated may have been as much as 0.1 g. This would be of consequence to some modern structures, designed without earthquake provisions.  相似文献   

The precise measurement of earth strain     

Ronald Green 《Tectonophysics》1974,23(4):361-371

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Enhancing RUSLE to include runoff‐driven phenomena     

Seth M. Dabney  Daniel C. Yoder  Dalmo A. N. Vieira  Ronald L. Bingner 《水文研究》2011,25(9):1373-1390

RUSLE2 (Revised Universal Soil Loss Equation) is the most recent in the family of Universal Soil Loss Equation (USLE)/RUSLE/RUSLE2 models proven to provide robust estimates of average annual sheet and rill erosion from a wide range of land use, soil, and climatic conditions. RUSLE2's capabilities have been expanded over earlier versions using methods of estimating time‐varying runoff and process‐based sediment transport routines so that it can estimate sediment transport/deposition/delivery on complex hillslopes. In this report we propose and evaluate a method of predicting a series of representative runoff events whose sizes, durations, and timings are estimated from information already in the RUSLE2 database. The methods were derived from analysis of 30‐year simulations using a widely accepted climate generator and runoff model and were validated against additional independent simulations not used in developing the index events, as well as against long‐term measured monthly rainfall/runoff sets. Comparison of measured and RUSLE2‐predicted monthly runoff suggested that the procedures outlined may underestimate plot‐scale runoff during periods of the year with greater than average rainfall intensity, and a modification to improve predictions was developed. In order to illustrate the potential of coupling RUSLE2 with a process‐based channel erosion model, the resulting set of representative storms was used as an input to the channel routines used in Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) to calculate ephemeral gully erosion. The method was applied to a hypothetical 5‐ha field cropped to cotton in Marshall County, MS, bisected by a potential ephemeral gully having channel slopes ranging from 0·5 to 5% and with hillslopes on both sides of the channel with 5% steepness and 22·1 m length. Results showed the representative storm sequence produced reasonable results in CREAMS indicating that ephemeral gully erosion may be of the same order of magnitude as sheet and rill erosion. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Multi-segment earthquakes and tsunami potential of the Aleutian megathrust     

Ian Shennan  Ronald Bruhn  George Plafker 《Quaternary Science Reviews》2009,28(1-2):7-13

Large to great earthquakes and related tsunamis generated on the Aleutian megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the Pacific Ocean. Here we use paleoseismic records preserved in coastal sediments to investigate whether segment boundaries control the largest ruptures or whether in some seismic cycles segments combine to produce earthquakes greater than any observed since instrumented records began. Virtually the entire megathrust has ruptured since AD1900, with four different segments generating earthquakes >M8.0. The largest was the M9.2 great Alaska earthquake of March 1964 that ruptured ～800 km of the eastern segment of the megathrust. The tsunami generated caused fatalities in Alaska and along the coast as far south as California. East of the 1964 zone of deformation, the Yakutat microplate experienced two >M8.0 earthquakes, separated by a week, in September 1899. For the first time, we present evidence that earthquakes ～900 and ～1500 years ago simultaneously ruptured adjacent segments of the Aleutian megathrust and the Yakutat microplate, with a combined area ～15% greater than 1964, giving an earthquake of greater magnitude and increased tsunamigenic potential.  相似文献