scholarly journals Hydrogeologic Property Estimation in Plate Boundary Observatory Boreholes Using Tidal Response Analysis

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jacob B. Simon ◽  
Patrick M. Fulton ◽  
Lian Xue
Keyword(s):  
Large Scale ◽  
Seismic Waves ◽  
Plate Boundary ◽  
Earth Tides ◽  
Cascadia Subduction Zone ◽  
Response Analysis ◽  
Specific Storage ◽  
Permeability Enhancement ◽  
Control Fluid ◽  
Pressure Changes

Because of the influence pore pressures have on effective stress, understanding hydrogeologic properties that control fluid flow and pressure distribution is important in characterizing earthquake and deformation processes. Here, we utilize borehole pressure changes in response to earth tides to determine hydrogeologic properties and their time variations for 17 boreholes within the NSF Earthscope’s Plate Boundary Observatory (PBO) network along the San Andreas fault and Cascadia subduction zone. Our analysis considers solutions for both confined and unconfined aquiares. Resulting permeability and hydraulic diffusivity values range from 6.4 × 10 − 16 – 8.4 × 10 − 14  m2 and 1 × 10 − 4 – 9 × 10 − 1   m 2 s − 1 , respectively, whereas specific storage values are generally ~ 1 × 10 − 6   m − 1 . The values are fairly consistent through time, reasonable given lithology, and are comparable to other regional studies. For one borehole, values are also comparable to those determined with traditional aquifer test data. In contrast with previous determinations of the high-frequency poroelastic response to seismic waves, no obvious spatial trends in hydrogeologic properties determined from long-wavelength tidal perturbations are observed. Within the recurring time-series estimates, only one borehole exhibits clear permeability enhancement by earthquakes, whereas nearby boreholes with similar lithology and hydrogeologic property values do not. This highlights the variable susceptibility of rocks to permeability enhancement. Together, these results provide quantitative constraints useful for models of large-scale groundwater flow around large fault systems and the potential hydrologic influence on deformation and fault slip behavior.

Elasto-Plastic Analysis of Seismic Response of Valve-Hall Structure with Suspension Valves of Large-Scale Converter Station

2011 ◽  
Vol 94-96 ◽  
pp. 1941-1945
Author(s):  
Yi Wu ◽  
Chun Yang ◽  
Jian Cai ◽  
Jian Ming Pan
Keyword(s):  
Seismic Response ◽  
Large Scale ◽  
Seismic Waves ◽  
Tensile Force ◽  
Response Analysis ◽  
Vertical Acceleration ◽  
Seismic Responses ◽  
Seismic Response Analysis ◽  
Finite Element Software ◽  
Plastic Analysis

Elasto-plastic analysis of seismic responses of valve hall structures were carried out by using finite element software, and the effect of seismic waves on the seismic responses of the valve hall structures and suspension equipments were studied. Results show that significant torsional responses of the structure can be found under longitudinal and 3D earthquake actions. Under 3D earthquake actions, the seismic responses of the suspension valves are much more significant than those under 1D earthquake actions, the maximum tensile force of the suspenders is about twice of that under 1D action. The seismic responses of the suspension valves under vertical earthquake actions are much stronger than those under horizontal earthquake actions, when suffering strong earthquake actions; the maximum vertical acceleration of the suspension valves is about 4 times of that under horizontal earthquake actions. It is recommended that the effects of 3D earthquake actions on the structure should be considered in seismic response analysis of the valve hall structure.

A new Python package to estimate hydraulic and poroelastic groundwater properties using standard pressure records

2021 ◽  
Author(s):  
Gabriel Rau ◽  
Daniel Schweizer ◽  
Chris Turnadge ◽  
Philipp Blum ◽  
Todd Rasmussen
Keyword(s):  
Earth Tide ◽  
Barometric Pressure ◽  
Earth Tides ◽  
Specific Storage ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
Barometric Efficiency ◽  
Standard Pressure ◽  
Pressure Changes ◽  
Python Package

<p>Determining subsurface hydraulic and geomechanical properties crucially underpins groundwater resource investigation and management. While standard practice relies on active testing, passive approaches require less effort and cost but are underutilised. We present the new Python package named HydroGeoSines (HGS) which quantifies hydraulic and poroelastic subsurface properties using the groundwater response to natural forces (such as Earth tides and atmospheric pressure changes) embedded in standard measurements. All implemented methods are drawn from the peer-reviewed literature. The package includes basic handling of time series, such as joining and aligning records and handling gaps. HGS uses standard atmospheric and groundwater pressure records to estimate the Barometric Response Function (BRF) groundwater state of confinement, hydraulic conductivity, specific storage, barometric efficiency (BE) and porosity. If Earth tides are required, they can be calculated on-the-fly using the PyGTide package which is based on ETERNA and included. HGS allows easy compensation and correction of pressure or hydraulic heads from barometric pressure or Earth tide influences. Further, HGS includes import from and export to common data formats as well as visualisation of data and results. We demonstrate the use of HGS using example datasets from around the world. Since HGS unlocks sophisticated methods for use by anyone with Python skills, we anticipate that it will support subsurface investigations and add value to standard monitoring practice.</p>

Simplified Criteria to Select Ground Response Analysis Methods for Seismic Building Design: Equivalent Linear versus Nonlinear Approaches

2021 ◽  
Author(s):  
Mauro Aimar ◽  
Sebastiano Foti
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Building Design ◽  
Soil Conditions ◽  
Response Analysis ◽  
Depth Range ◽  
Ground Response Analysis ◽  
Equivalent Linear ◽  
Acceleration Time Histories ◽  
Soil Deposits

ABSTRACT The possible amplification of seismic waves in soil deposits is crucial for the seismic design of buildings and geotechnical systems. The most common approaches for the numerical simulation of seismic site response are the equivalent linear (EQL) and the nonlinear (NL). Even though their advantages and limitations have been investigated in several studies, the relative field of applicability is still under debate. This study tested both methods over a wide population of soil models, which were subjected to a set of acceleration time histories recorded from strong earthquakes. A thorough comparison of the results of the EQL and the NL approaches was carried out, to identify the conditions in which the relative differences are significant. This assessment allowed for the definition of simplified criteria to predict when the two schemes are or are not compatible for large expected shaking levels. The proposed criteria are based on simple and intuitive parameters describing the soil deposit and the ground-motion parameters, which can be predicted straightforwardly. Therefore, this study provides a scheme for the choice between the EQL and the NL approaches that can be used even at the preliminary design stages. It appears that the EQL approach provides reliable amplification estimates in soil deposits with thickness up to 30 m, except for very deformable soils, but this depth range may be extended at long vibration periods. This result reveals a good level of reliability of the EQL approach for various soil conditions encountered in common applications, even for high-intensity shaking.

scholarly journals Numerical modeling of seismic waves by discontinuous spectral element methods

2018 ◽  
Vol 61 ◽  
pp. 1-37 ◽  
Author(s):  
Paola F. Antonietti ◽  
Alberto Ferroni ◽  
Ilario Mazzieri ◽  
Roberto Paolucci ◽  
Alfio Quarteroni ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Discontinuous Galerkin ◽  
Large Scale ◽  
Seismic Waves ◽  
Spectral Element ◽  
Fully Discrete ◽  
Time Marching ◽  
Space Discretization ◽  
Large Earthquakes

We present a comprehensive review of Discontinuous Galerkin Spectral Element (DGSE) methods on hybrid hexahedral/tetrahedral grids for the numerical modeling of the ground motion induced by large earthquakes. DGSE methods combine the exibility of discontinuous Galerkin meth-ods to patch together, through a domain decomposition paradigm, Spectral Element blocks where high-order polynomials are used for the space discretization. This approach allows local adaptivity on discretization parameters, thus improving the quality of the solution without affecting the compu-tational costs. The theoretical properties of the semidiscrete formulation are also revised, including well-posedness, stability and error estimates. A discussion on the dissipation, dispersion and stability properties of the fully-discrete (in space and time) formulation is also presented. Here space dis-cretization is obtained based on employing the leap-frog time marching scheme. The capabilities of the present approach are demonstrated through a set of computations of realistic earthquake scenar-ios obtained using the code SPEED (http://speed.mox.polimi.it), an open-source code specifically designed for the numerical modeling of large-scale seismic events jointly developed at Politecnico di Milano by The Laboratory for Modeling and Scientific Computing MOX and by the Department of Civil and Environmental Engineering.

scholarly journals The Gujarat, West India, earthquake (Jan 26th 2001). A geodynamic event in an intraplate compressional regime?

2001 ◽  
Vol 34 (4) ◽  
pp. 1405
Author(s):  
Γ. Δ. ΔΑΝΑΜΟΣ ◽  
Ε. Λ. ΛΕΚΚΑΣ ◽  
Σ. Γ. ΛΟΖΙΟΣ
Keyword(s):  
Large Scale ◽  
Lateral Displacement ◽  
Indian Subcontinent ◽  
Plate Boundary ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Lateral Spreading ◽  
Tectonic Deformation ◽  
Epicentral Area ◽  
Surface Ruptures

The Jan. 26, 2001, Ms=7.7 earthquake occurred in Gujarat region of W. India, which lies 200-400 Km away from the active plate boundary zone, between the Indian subcontinent and the Asian plate, along the India-Pakistan border and the Himalayan belt. An Ms=7.7±0.2 earthquake also occurred in the same region in 1819. A zone of co-seismic E-W surface ruptures, 30-40 Km long and 15-20 Km wide, observed near the epicentral area and seems to be associated with pre-existing reverse faults and thrust folds, which were partially reactivated during the recent earthquake. Except the reverse vertical displacement a significant right lateral displacement was also observed along these E-W surface ruptures. This Ms=7.7 seismic event has been also accompanied by a large scale flexural-slip folding, as the absence of significant co-seismic fault displacement and fault scarp shows. This type of compressional tectonic deformation is also confirmed by the focal mechanism of the earthquake and the seismo-tectonic "history" of the area. The NW-SE open cracks, also observed along the same zone, are associated with the right lateral horizontal displacement of the reactivated fault (or branch faults) and the development of local extensional stress field in the huge anticlinic hinges of the co-seismic flexural-slip folds. A large number of ground ruptures, failures and open cracks are also associated with extensive sand boils, liquefaction phenomena and lateral spreading.

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