scholarly journals Gas hydrate concentration estimates from chlorinity, electrical resistivity and seismic velocity

2005 ◽  
Author(s):  
M Riedel ◽  
T S Collett ◽  
R D Hyndman
Keyword(s):  
Electrical Resistivity ◽  
Gas Hydrate ◽  
Seismic Velocity

Geophysical characterization of inactive/active rock glaciers in the semi-arid Andes using seismic, geoelectrics and GPR

2020 ◽  
Author(s):  
remi valois ◽  
Nicole Schafer ◽  
Giulia De Pasquale ◽  
Gonzalo Navarro ◽  
Shelley MacDonell
Keyword(s):  
Electrical Resistivity ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Late Summer ◽  
Relevant Information ◽  
Refraction Tomography ◽  
Rock Glaciers ◽  
Ice Content ◽  
Ground Penetrating

<p>Rock glaciers play an important hydrological role in the semiarid Andes (SA; 27º-35ºS). They cover about three times the area of uncovered glaciers and they are an important contribution to streamflow when water is needed most, especially during dry years and in the late summer months. Their characteristics such as their extension in depth and their ice content is poorly known. Here, we present a case study of one active rock glacier and periglacial inactive geoform in Estero Derecho (~30˚S), in the upper Elqui River catchment, Chile. Three geophysical methods (ground-penetrating radar and electrical resistivity and seismic refraction tomography) were combined to detect the presence of ice and understand the internal structure of the landform. The results suggest that the combination of electrical resistivity and seismic velocity provide relevant information on ice presence and their geometry. Radargrams shows diffraction linked to boulders presence but some information regarding electromagnetic velocity could be extracted. These results strongly suggest that such landforms contain ice, are therefore important to include in future inventories and should be considered when evaluating the hydrological importance of a particular region.</p><p> </p>

scholarly journals Assessment of gas-hydrate saturations in the Makran accretionary prism using the offset dependence of seismic amplitudes

Geophysics ◽  
2010 ◽  
Vol 75 (2) ◽  
pp. C1-C6 ◽  
Author(s):  
Maheswar Ojha ◽  
Kalachand Sain ◽  
Timothy A. Minshull
Keyword(s):  
Gas Hydrate ◽  
Seismic Velocity ◽  
Rock Physics ◽  
Accretionary Prism ◽  
Seismic Line ◽  
Amplitude Variation With Offset ◽  
Free Gas ◽  
Bottom Simulating Reflector ◽  
Physics Modeling ◽  
Physics Model

We estimate the saturations of gas hydrate and free gas based on measurements of seismic-reflection amplitude variation with offset (AVO) for a bottom-simulating reflector coupled with rock-physics modeling. When we apply the approach to data from a seismic line in the Makran accretionary prism in the Arabian Sea, the results reveal lateral variations of gas-hydrate and free-gas saturations of 4–29% and 1–7.5%, respectively, depending on the rock-physics model used to relate seismic velocity to saturation. Our approach is simple and easy to implement.

scholarly journals Assessment results of soil properties by engineering-geophysical studies

2021 ◽  
Author(s):  
Дж.К. Карапетян ◽  
А.З. Чилингарян ◽  
К.А. Карапетян ◽  
Г.А. Мкртчян
Keyword(s):  
Electrical Resistivity ◽  
Seismic Velocity ◽  
Gas Storage ◽  
Seismic Intensity ◽  
Excitation Power ◽  
Soil Conditions ◽  
Compressor Station ◽  
Underground Gas Storage ◽  
Seismic Properties ◽  
Seismic Receiver

В статье излагаются результаты инженерно-геофизических исследований на территории новой компрессорной станции Специального подземного хранилища газа (СПХГ) в г. Абовян (Армения). Учитывая то, что Республика Армения находится в сейсмоактивной зоне, проведение данных исследований является весьма актуальными, а новая компрессорная станция Специального подземного хранилища газа является особо важным объектом. Целью работы является выявление для данной территории особенности удельного электрического сопротивления грунтов, наличие блуждающих токов (БТ), оценка коррозийной агрессивности грунтов, изучение сейсмических условий и оценка ожидаемой сейсмической интенсивности на территории, намеченной под строительство. Методы работы. Определение удельного (кажущегося) электрического сопротивления грунтов исследуемой территории производилось методом электропрофилирования с использованием симметричной четырехэлектродной установки Веннера. В статье представлены пункты измерения удельного электрического сопротивления грунтов на территории новой компрессорной станции Абовянского СПХГ, выявлено наличие блуждающих токов, приведены таблицы степени коррозионной агрессивности грунтов, указаны места наличия опасного уровня блуждающих токов. Также проведены работы по сейсмическому микрорайонированию для определения величины ожидаемой сейсмической интенсивности конкретной территории компрессорной станции. Ожидаемая сейсмическая интенсивность на данной территории определена на основе анализа инженерно-геологических материалов с учетом результатов полевых инженерно-сейсмометрических инструментальных исследований. С помощью малоглубинной сейсморазведки были определены скорости распространения сейсмических волн. Измерения проводились горизонтально-ориентированным сейсмоприемником СМ-3 (вертикальный удар). Ударные волны создавались импульсным возбуждением. Для обеспечения необходимой мощности возбуждения импульсное воздействие создавалась с помощью падающего груза. Результаты работы. В статье приведены сейсмические условия территории, результаты сейсмометрических исследований,данные по наблюдениям микросейсм, спектры Фурье преобладающих периодов по некоторым точкам наблюдений, схема инженерно-сейсмометрических наблюдений. В результате проведенных исследований установлено, что грунтовые условия данной территории относятся к грунтам первой категории по сейсмическим свойствам. Ожидаемую сейсмическую опасность исследованной территории необходимо характеризовать следующими значениями: I=7 баллов или PGA=0,24 g. The article presents the results of engineering-geophysical studies on the territory of the new compressor station of the Special Underground Gas Storage (SPGS) in the city of Abovyan (Armenia). Considering that the Republic of Armenia is located in a seismically active zone, these studies are highly relevant, and the new compressor station of the Special Underground Gas Storage is especially important object. The Aim of the presented work is to identify the features of the specific electrical resistivity of soils, the presence of stray currents, assess the corrosive aggressiveness of soils, seismic conditions of the territory and the expected seismic intensity in the area designated for construction. Methods. The determination of the specific (apparent) electrical resistivity of the soils of the study area was carried out by the method of electrical profiling using symmetrical four-electrode Wenner setup. The article presents the points of measuring the electrical resistivity of soils in the territory of the new compressor station of the Abovyan SPGS, revealed the presence of stray currents, tables of the degree of corrosiveness of soils are given, the locations of the presence of a dangerous level of stray currents are indicated. Also works on seismic microzoning were carried out, the values of the expected seismic intensity of the compressor station territory were determined. The expected seismic intensity in this area has been determined based on analysis of engineering-geological materials, taking into account the results of field engineering-seismometric instrumental studies. By using shallow seismic surveys have determined the speed of seismic velocity. Measurements were carried out horizontally oriented seismic receiver SM-3 (vertical impact). Shock waves were generated by pulsed excitation. To provide the required excitation power the impulse action was created using a falling weight. Results. The article presents the seismic conditions of the territory, the results of seismometric studies, data on observations of microseisms, Fourier spectra of prevailing periods for some observation points, a scheme of engineering seismometric observations. As a result of the research carried out, it was found that that the soil conditions composing this territory belong to the soils of the first category in terms of seismic properties, the expected seismic hazard of the investigated area should be taken as I = 7 points or PGA = 0.24 g.

scholarly journals Electrical Resistivity Measurements On The Ross Ice Shelf

1977 ◽  
Vol 18 (78) ◽  
pp. 15-35 ◽  
Author(s):  
Charles R. Bentley
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Seismic Velocity ◽  
Sea Water ◽  
Field Measurements ◽  
Ice Shelf ◽  
Glacial Ice ◽  
Resistivity Measurements ◽  
Ross Ice Shelf ◽  
The North

AbstractElectrical resistivity measurements were made along two perpendicular profiles on the Ross Ice Shelf, Antarctica, in 1973–74. Apparent resistivities are generally well determined at electrode separations from 10 m out to 600 m, where the effect of the highly conducting sea-water beneath the shelf becomes strongly fell. Schlumberger and equatorial-dipole data are in excellent agreement on each profile; apparent resistivities on the two profiles, however, differ by about 12% at separations greater than about 30 m. This apparent anisotropy is attributed to a presumed inhomogeneity at a few tens of meters depth, rather than to true anisotropy in the bulk resistivity.A computer program has been developed to calculate apparent resistivities on an ice shelf in which the density and temperature, and thus the resistivity, vary continuously with depth. Temperatures have been calculated according to the analysis of Crary (1961 [b]) for a steady-state ice shelf; densities have been calculated from seismic velocity data. Several different models of the dependence of resistivity on density have been tested—one appears to fit the observations very closely, but it must be accepted only with great caution because the assumptions on which it is based are violated in the ice shelf.The activation energy and the rate of bottom melting or freezing upon which the temperature-depth variations depend have been treated as variable parameters in the modeling. The most satisfactory model corresponds to a melt/freeze rate close to zero, and an activation energy, 0.25 eV (24 kJ mol−1), in agreement with laboratory measurements on Antarctic ice samples, although less than that suggested by previous field measurements. However, since the actual temperatures in the ice shelf are unknown, models that combine a substantial melt rate with a higher activation energy, or a substantial freeze rate with a lower activation energy, cannot be ruled out at present. Future measurements in places where the temperature profile is known should resolve this uncertainty.The actual resistivity in the solid ice at a depth of about 100 m (temperature about —23°C), lies within ±10% of 70000 Ω m, thus once again confirming the very low resistivities typical of polar glacial ice. The resistivity is, in fact, only about half that found near Roosevelt Island to the north and “Byrd” station to the east. That difference is believed to be real, but its cause is not known and probably will not be known until the basic cause for the generally low resistivity of polar ice is better understood.

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