scholarly journals Magnetotelluric regional strike

Geophysics ◽  
1982 ◽  
Vol 47 (6) ◽  
pp. 932-937 ◽  
Author(s):  
T. D. Gamble ◽  
W. M. Goubau ◽  
R. Miracky ◽  
J. Clarke
Keyword(s):  
Baja California ◽  
Weighting Function ◽  
Three Dimensional ◽  
Geothermal Field ◽  
New Method ◽  
Weighted Sums ◽  
Impedance Tensor ◽  
Two Dimensional ◽  
Cerro Prieto

A new method for determining regional strikes from the magnetotelluric impedance tensor Z and tipper T is presented. It involves the minimization of weighted sums of the squared magnitudes of elements of Z or T over all frequencies and all stations of interest. When applied to data from the Mexicali Valley, Baja California around the Cerro Prieto geothermal field for a particular weighting function, the method yielded orientations that agree to within 2.9 degrees for three lines with a total of 16 stations. The consistency of orientations can be attributed in part to the pronounced two‐dimensional (2-D) geologic characteristics of the area, but the techniques also proved stable at stations near three‐dimensional (3-D) inhomogeneities.

scholarly journals Three-Dimensional Coordination Number from Two-Dimensional Measurements: A New Method

1986 ◽  
Vol 32 (112) ◽  
pp. 391-396 ◽  
Author(s):  
Richard B. Alley
Keyword(s):  
Coordination Number ◽  
Three Dimensional ◽  
New Method ◽  
Two Dimensional ◽  
Shape Factors ◽  
Important Measure ◽  
Dimensional Measurements ◽  
Average Bond

AbstractThe average three-dimensional coordination number, n3, is an important measure of firn structure. The value of n3 can be estimated from n2, the average measured two-dimensional coordination number, and from a function, Γ, that depends only on the ratio of average bond radius to grain radius in the sample. This method is easy to apply and does not require the use of unknown shape factors or tunable parameters.

Groundwater exploration using combined controlled-source and radiomagnetotelluric techniques

Geophysics ◽  
2005 ◽  
Vol 70 (1) ◽  
pp. G8-G15 ◽  
Author(s):  
Laust B. Pedersen ◽  
M. Bastani ◽  
L. Dynesius
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Groundwater Exploration ◽  
Impedance Tensor ◽  
Two Dimensional ◽  
Controlled Source ◽  
Reflection Seismic ◽  
Seismic Sections ◽  
Clay Layers ◽  
Clay Lenses

Radiomagnetotelluric (RMT) (14–250 kHz) combined with controlled-source magnetotelluric (CSMT) (1–12 kHz) measurements were applied to the exploration of groundwater located in sandy formations at depths as great as 20 m below thick clay lenses. A combination of approximately 30 radio frequencies and controlled-source frequencies is essential for penetrating the thick clay layers. The electromagnetic transfer functions of impedance tensor and tipper vectors point toward a structure that is largely two-dimensional, although clear three-dimensional effects can be observed where the sandy formation is close to the surface. The determinant of the impedance tensor was chosen for inversion using two-dimensional models. The final two-dimensional model fits the data to within twice the estimated standard errors, which is considered quite satisfactory, given that typical errors are on the level of 1% on the impedance elements. Comparison with bore-hole results and shallow-reflection seismic sections show that the information delivered by the electromagnetic data largely agrees with the former and provides useful information for interpreting the latter by identifying lithological boundaries between the clay and sand and between the sand and crystalline basement.

scholarly journals A new method to estimate point thermal transmittance based on combined two-dimensional heat flow calculation

2020 ◽  
Vol 172 ◽  
pp. 08005
Author(s):  
Jaanus Hallik ◽  
Targo Kalamees
Keyword(s):  
Heat Flow ◽  
Three Dimensional ◽  
Multiple Linear Regression Model ◽  
Building Envelope ◽  
New Method ◽  
Two Dimensional ◽  
Thermal Transmittance ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
Third Dimension

A well-insulated, airtight and thermal bridge free building envelope is a key factor for nearly zero energy buildings (nZEB). However, increased insulation thickness and minimized air leakages increase the effect of thermal bridges on overall energy efficiency of the nZEBs. Although several more prominent linear thermal bridges are accounted for in the practice the three-dimensional heat flow through vast array of fixation elements, mounting brackets and other point thermal bridges are usually neglected due to time-consuming model preparation routine, lack of input data as well as high number of different thermal bridges that have to be assessed for a single project. In this study a new method was proposed for predicting three-dimensional heat flow and the point thermal transmittance of thermal bridges caused by full or partial penetration of the building envelope with metal elements with uniform geometry in third dimension based on multiple two-dimensional numerical heat flow calculations. A new parameter (equivalent length of thermal bridge) was defined which incorporates the effect of additional thermal transmittance in third dimension when multiplied by the difference of two thermal coupling coefficients derived for two-dimensional cross section. Multiple linear regression model was fitted on database with 102 cases and verified with separate case of window to wall connection incorporating metal penetration at fixation points. The proposed methodology can be useful in general practice where the design team lacks the skills or software tools for conducting detailed numerical analysis in three dimensions.

Beamtrees: Compact Visualization of Large Hierarchies

2003 ◽  
Vol 2 (1) ◽  
pp. 31-39 ◽  
Author(s):  
Frank van Ham ◽  
Jarke J. van Wijk
Keyword(s):  
Hierarchical Structure ◽  
User Study ◽  
Three Dimensional ◽  
New Method ◽  
Data Sets ◽  
Two Dimensional ◽  
Hierarchical Data ◽  
Organization Structures ◽  
The Hierarchical Structure

Beamtrees are a new method for the visualization of large hierarchical data sets, such as directory structures and organization structures. Nodes are shown as stacked circular beams such that both the hierarchical structure as well as the size of nodes are depicted. The dimensions of beams are calculated using a variation of the treemap algorithm. Both a two-dimensional and a three-dimensional variant are presented. A small user study indicated that beamtrees are significantly more effective than nested treemaps and cushion treemaps for the extraction of global hierarchical information.

scholarly journals Spatio-temporal evolution of aseismic ground deformation in the Mexicali Valley (Baja California, Mexico) from 1993 to 2010, using differential SAR interferometry

2015 ◽  
Vol 372 ◽  
pp. 335-341 ◽  
Author(s):  
O. Sarychikhina ◽  
E. Glowacka
Keyword(s):  
Deformation Rate ◽  
Baja California ◽  
Temporal Evolution ◽  
Ground Deformation ◽  
Geothermal Field ◽  
Sar Interferometry ◽  
Deformation Pattern ◽  
Ground Fissures ◽  
Spatio Temporal ◽  
Cerro Prieto

Abstract. Ground deformation in Mexicali Valley, Baja California, Mexico, the southern part of the Mexicali-Imperial valley, is influenced by active tectonics and human activity, mainly that of geothermal fluid extraction in the Cerro Prieto Geothermal Field. Significant ground deformation, mainly subsidence (~ 18 cm yr−1), and related ground fissures cause severe damage to local infrastructure. The technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) has been demonstrated to be a very effective remote sensing tool for accurately measuring the spatial and temporal evolution of ground displacements over broad areas. In present study ERS-1/2 SAR and ENVISAT ASAR images acquired between 1993 and 2010 were used to perform a historical analysis of aseismic ground deformation in Mexicali Valley, in an attempt to evaluate its spatio-temporal evolution and improve the understanding of its dynamic. For this purpose, the conventional 2-pass DInSAR was used to generate interferograms which were used in stacking procedure to produce maps of annual aseismic ground deformation rates for different periods. Differential interferograms that included strong co-seismic deformation signals were not included in the stacking and analysis. The changes in the ground deformation pattern and rate were identified. The main changes occur between 2000 and 2005 and include increasing deformation rate in the recharge zone and decreasing deformation rate in the western part of the CPGF production zone. We suggested that these changes are mainly caused by production development in the Cerro Prieto Geothermal Field.

Attenuation of coda waves at the Cerro Prieto geothermal field, Baja California, Mexico

1997 ◽  
Vol 87 (5) ◽  
pp. 1368-1374
Author(s):  
Tonatiuh Domínguez ◽  
Cecilio J. Rebollar ◽  
Hubert Fabriol
Keyword(s):  
Baja California ◽  
Hot Springs ◽  
Single Scattering ◽  
Geothermal Field ◽  
Coda Waves ◽  
S Wave ◽  
Low Frequencies ◽  
S Waves ◽  
A Value ◽  
Cerro Prieto

Abstract We analyzed coda waves from 22 local events recorded by a temporary network of seismic stations deployed in the Cerro Prieto geothermal field of Baja California, Mexico, to estimate coda attenuation Qc in the frequency range 6 to 24 Hz. We used Sato's (1977) single scattering model for a coda window of 12.5 ± 2.5 sec beginning at twice the S-wave travel time. All events analyzed were located within the exploitation area with depths up to 6 km and source-to-receiver distances less than 8 km. At frequencies of 3, 4, and 5 Hz, rms amplitudes of coda to S waves showed no clear decay or even negative Qc values. This could be due to the inability of the theory to fit the data at low frequencies as it was suggested by Fehler et al. (1992). Within the range of variation, five of the seven stations showed similar Qc values that ranged from about 200 at 6 Hz to about 490 at 24 Hz. Assuming a power-law dependence of the form Qc (ƒ) = Q0ƒη, we estimated a value of Q0 = 111.5 ± 23 and a frequency dependence η of 0.41 ± 0.1. We found site effects at two stations that were located close to hot springs and mud pools.

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