Most earthquake location methods require phase identification and arrival-time measurements. These are generally fast efficient but not always applicable to microearthquake data with low signal-to-noise ratios because the might be very difficult. The migration-based source methods, which do an explicit identification, often more suitable for such noisy data. Whereas some existing computationally intensive, others limited a certain type of or make use only particular signal. We have developed...

The numerical simulation of gravity perturbations associated with deep slab deformations during the seismic cycle great subduction earthquakes remains a significant challenge. This study presents novel approach for simulating anomalies induced by short-term using Spectral-Infinite-Element (SIE) method, implemented in SPECFEM-X tool. Geodynamic models involving different fault settings are developed within realistic 3D earth structure. includes layer infinite boundary elements surrounding...

SUMMARY We implement a spectral‐element method for 3D time‐independent elastoplastic problems in geomechanics. As first application, we use the slope stability analyses ranging from small to large scales. The implementation employs an element‐by‐element preconditioned conjugate‐gradient solver efficient storage. program accommodates material heterogeneity and complex topography. Either simple or water table profiles may be used assess effects of hydrostatic pressure. Both surface loading...

We use time‐reversal imaging for microearthquake location and investigate the possibility of a simultaneous qualitative moment‐tensor estimation. cross‐correlate data with synthetic strain Green's tensor stack individually each component. The objective function source is then formulated as squared sum those stacked components. maximum value corresponds to estimated origin time. Similarly, corresponding components at give entire time history estimation moment tensor. apply method various...

Gravity anomalies induced by density heterogeneities are governed Poisson's equation. Most existing methods for modelling such rely on its integral solution. In this approach, each observation point, an over the entire distribution needs to be carried out, and computational cost is proportional number of points. Frequently, sensitive high contrasts due inaccurate resolution volume integral. We introduce a new approach which directly solves discretized form Poisson/Laplace The main challenge...

Knowledge of deformation at plate boundaries has been improved greatly by the development observational techniques in space geodesy. However, most theoretical and numerical models coseismic have remained very simple do not include realistic Earth structure. 3-D material heterogeneity topography are often neglected because assumed to be sufficient available tools cannot easily accommodate complex heterogeneity. In this study, we demonstrate importance using a spectral element method that...

Microseismic monitoring of hydraulic fractures is an important tool for imaging fracture networks and optimizing the reservoir engineering stimulation. The range magnitudes recorded microseisms depends at lower limit on array sensitivity; while upper varies significantly from site to site. In this paper variation in microseismic magnitude examined compared with injection characteristics. Although there are numerous potential factors effecting seismic deformation, energy pumping state stress...

Although earthquake-induced gravity perturbations are frequently observed, numerical modelling of this phenomenon has remained a challenge. Due to the lack reliable and versatile tools, induced-gravity data have not been fully exploited constrain earthquake source parameters. From perspective, main challenge stems from unbounded Poisson/Laplace equation that governs perturbations. Additionally, must be coupled with conservation linear momentum particle displacement in solid. Most existing...

Accurate and efficient simulations of coseismic post-earthquake deformation are important for proper inferences earthquake source parameters subsurface structure. These often performed using a truncated half-space model with approximate boundary conditions. The use such conditions introduces inaccuracies unless sufficiently large is used, which greatly increases the computational cost. To solve this problem, we develop new approach by combining spectral-element method mapped infinite-element...

We solve Poisson's equation by combining a spectral-element method with mapped infinite-element method. focus on problems in geostatics and geodynamics, where Earth's gravitational field is determined inside the Earth Laplace's rest of space. Spectral elements are used to capture internal field, infinite represent external field. To weak form Poisson/Laplace equation, we use Gauss-Legendre-Lobatto quadrature spectral domain interest. Outside domain, Gauss-Radau direction, other directions....

Abstract Accurate and efficient forward modeling methods are important for simulation of seismic wave propagation in 3D realistic Earth models crucial high‐resolution full waveform inversion. In the presence attenuation, wavefield could be inaccurate or unstable over time if not well treated, indicating importance implementation a strong stability preserving discretization scheme. this study, to solve anelastic equation, we choose optimal Runge‐Kutta (SSPRK) method temporal apply...

We implement a spectral-infinite-element method (SIEM) to compute magnetic anomalies by solving discretized form of the Poisson/Laplace equation. The SIEM combines highly accurate spectral-element with mapped-infinite element method, which reproduces an unbounded domain accurately and efficiently. This combination is made possible coupling Gauss–Legendre–Lobatto quadrature in spectral elements Gauss–Radau infinite along directions. Our has two distinct advantages over traditional methods....

Gas extraction from the Groningen natural gas field, situated in Netherlands, frequently induces earthquakes reservoir that cause damage to buildings, and pose a safety hazard nuisance local population. Due dependence of national heating infrastructure on gas, short-term mitigation measures are mostly limited combination spatiotemporal redistribution production strengthening for buildings. All options become more effective with better understanding both source processes seismic wave...

SUMMARY Although observation of gravity perturbations induced by earthquakes is possible, simulation seismic wave propagation in a self-gravitating, rotating Earth model with 3-D heterogeneity challenging due to the numerical complexities associated unbounded Poisson/Laplace equation that governs perturbations. Therefore, are generally omitted, and only background taken into account using so-called Cowling approximation. However, may be significant for large (Mw ≥ 6.0) long-period responses....

We compute P‐ and S‐wave first arrival times for a heterogeneous model of the Pyhäsalmi ore mine using finite‐difference Eikonal code (Podvin Lecomte, 1991). For very same we are computing complete wavefield viscoelastic finite difference scheme (Larsen Schultz, 1995). compare synthetic results amongst each other with real microseismic data recorded an in‐mine seismic network. The resulting generally agree onset wavefield, whereas amplitude distribution is strongly affected by...

A laboratory experiment has been conducted on a sandstone sample where small hole drilled through the middle of sample. The intention is to simulate borehole breakout effects and observe non‐ double couple acoustic emission events. We then determine full moment tensors for data from tri‐ axial experiment. tensor inversion uses first motion polarity amplitude information as input parameters. observed are compared with synthetic Spectral Element Method simulation using hexahedron elements,...

Summary In a migration-based approach used for detection and location of weak microseismic activity, key issue to look at is the expected focusing pattern network, with respect given velocity model according selected phases (e.g., first arrivals). Such patterns can be estimated by so-called Point-Spread Functions (PSFs), as adapted from similar technology in active seismic. The PSFs will represent 3D spatial resolution problem, independently any data their errors. It thus prior recording,...

In this study, we model acoustic waves induced by moving sources in three-dimensional (3D) underwater settings based on a spectral-element method (SEM). Numerical experiments are conducted using the SEM software package SPECFEM3D_Cartesian, which facilitates fluid–solid coupling and absorbing boundary conditions. Examples presented paper include an unbounded fluid truncated boundaries, shallow-water waveguide modeled as coupled system domain decomposition. numerical experiments, SEM-computed...

Currently, the accuracy of synthetic seismograms used for Global CMT inversion, which are based on modern 3D Earth models, is limited by validity path-average approximation mode summation and surface-wave ray theory. Inaccurate computation ground motion’s amplitude polarization as well other effects that not modeled may bias inverted earthquake parameters. Synthetic higher will improve determination seismic sources in analysis, remove concerns about this source uncertainty. Strain...

We show how the linearized equations that govern motion of a body undergoes deformation can be generalized to capture geometrical non-linearities in spectral-element formulation. Generalizing adds little complexity, main addition being we have track gradient. Geometrical changes due are captured using logarithmic strain. test geometrically non-linear formulation by considering numerical experiments seismic wave propagation and cantilever beam bending compare results with In cases where...

Pile driving is used for constructing foundation supports offshore structures. Underwater noise, induced by in-water pile driving, could adversely impact marine life near the piling location. Many studies have computed this noise in close ranges using semi-analytical models and Finite Element Method (FEM) models. This work presents a Spectral (SEM) wave simulator as an alternative simulation tool to obtain close-range underwater complex, fully three-dimensional, axially-asymmetric settings...