DSpace Angular :: Browsing by Author "Crempien, Jorge G. F."

Browsing by Author "Crempien, Jorge G. F."

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A comparison of ground motions predicted through one-dimensional site response analyses and three-dimensional wave propagation simulations at regional scales
(2024) Zhang, Wenyang; Dong, Yufeng; Crempien, Jorge G. F.; Arduino, Pedro; Kurtulus, Asli; Taciroglu, Ertugrul
One-dimensional (1D) site response analysis (SRA), which considers vertically propagating seismic waves from the bedrock to the surface, has been a common technique among geotechnical engineers to examine site-specific ground shaking. However, observations from past earthquakes and analytical studies indicate that idealizations ingrained in 1D SRA may be too severe to capture the ground truth, such as the omissions of spatial variability of soil properties, surface topography, and basin and directivity effects. Physics-based three-dimensional ground motion simulations (GMSs) can incorporate these factors and yield more reliable predictions. In this study, we utilize ground motions from 57 physics-based broadband (from 0 to 8-12 Hz) GMS for a region of Istanbul. A total of 2912 sites with experimentally measured soil profiles that are distributed over the 30 km-by-12.5 km area are also modeled as soil columns and analyzed through 1D SRA. The ground responses from 1D SRA and three-dimensional (3D) GMS are then compared for all 57 earthquake scenarios. These systematic comparisons are then used for examining model features that are correlated with variations in the ratios of various ground motion intensity measures (IMs) and for developing regression-based formulas that can be used for determining simple factors for the considered region to correctly scale (up or down) the site-specific ground motion intensities obtained from 1D SRA, including peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration (Sa) values.
A proxy implementation of thermal pressurization for earthquake cycle modelling on rate-and-state faults
(2024) Herrera, Marco T.; Ampuero, Jean P.; Crempien, Jorge G. F.
The reduction of effective normal stress during earthquake slip due to thermal pressurization of fault zone pore fluids is a significant fault weakening mechanism. Explicit incorporation of this process into frictional fault models involves solving the diffusion equations for fluid pressure and temperature outside the fault at each time step, which significantly increases the computational complexity. Here, we propose a proxy for thermal pressurization implemented through a modification of the rate-and-state friction law. This approach is designed to emulate the fault weakening and the relationship between breakdown energy and slip resulting from thermal pressurization and is appropriate for fully dynamic simulations of multiple earthquake cycles. It preserves the computational efficiency of conventional rate-and-state friction models, which in turn can enable systematic studies to advance our understanding of the effects of fault weakening on earthquake mechanics. In 2.5-D simulations of pulse-like ruptures on faults with finite seismogenic width, based on our thermal pressurization proxy, we find that the spatial distribution of slip velocity near the rupture front is consistent with the conventional square-root singularity, despite continued slip-weakening within the pulse, once the rupture has propagated a distance larger than the rupture width. An unconventional singularity appears only at shorter rupture distances. We further derive and verify numerically a theoretical estimate of the breakdown energy dissipated by our implementation of thermal pressurization. These results support the use of fracture mechanics theory to understand the propagation and arrest of very large earthquakes.
A suite of broadband physics-based ground motion simulations for the Istanbul region
(2023) Zhang, Wenyang; Crempien, Jorge G. F.; Kurtulus, Asli; Chen, Peng-Yu; Arduino, Pedro; Taciroglu, Ertugrul
Physics-based earthquake ground motion simulations (GMS) have acquired significant growth over the last two decades, mainly due to the explosive developments of high-performance computing techniques and resources. These techniques benefit high/medium seismicity regions such as the city of Istanbul, which presents insufficient historical ground motion data to properly estimate seismic hazard and risk. We circumvent this reality with the aid of the Texas Advanced Computing Center (TACC) facilities to perform a suite of 57 high-fidelity broadband (8-12 Hz) large-scale physics-based GMS for a region in Istanbul, Turkey. This paper focuses on the details of simulated GMS: (i) validation of the GMS approach against recorded ground motions produced by the 2019 Mw5.7$M_{w}\nobreakspace 5.7$ Silivri earthquake; (ii) characteristics of 57 different source models, which aim to consider the uncertainties of many fault rupture features, including the length and width, dip, strike, and rake angles of considered fault planes, as well as hypocenter locations and earthquake magnitudes ranging between Mw$M_{w}$ 6.5 and 7.2; (iii) high-resolution topography and bathymetry and seismic data that are incorporated into all GMS; (iv) simulation results, such as PGAs and PGVs versus Vs30$V_{s30}$ and distances to fault ruptures (Rrup$R_{\text{rup}}$), of 2912 surface stations for all 57 GMS. More importantly, this research provides a massive database of displacement, velocity and acceleration time histories in all three directions over more than 20,000 stations at both surface and bedrock levels. Such site-specific high-density and -frequency simulated ground motions can notably contribute to the seismic risk assessment of this region and many other applications.
"Bristle-State" Friction: Modeling Slip Initiation and Transient Frictional Evolution From High-Velocity Earthquake Rupture Experiments
(2020) Saltiel, Seth; Mittal, Tushar; Crempien, Jorge G. F.; Campos, Jaime
Fracture mechanics theory and seismological observations suggest that slip-rate is constantly changing during earthquake rupture, including dramatic acceleration from static conditions to high velocity sliding followed by deceleration and arrest. This slip history is partly determined by a complex frictional evolution, including overcoming peak friction, rapid weakening, and re-strengthening (or healing). Recent experimental developments have allowed friction evolution measurements under realistic slip histories reaching high co-seismic slip-rates of meters per second. Theoretical work has focused on describing the observed steady-state weakening at these high-velocities, but the transient behavior has only been fit by direct parameterizations without state variable dependence, needed to simulate arbitrary slip-histories. Commonly used forms of rate-state friction (RSF) are based on low-velocity, step-change experiments and have been shown to not fit the entire frictional evolution using a single set of realistic parameters. Their logarithmic form precludes zero fault slip-rate, assuming it is never truly static, thus does not capture slip initiation phenomena that might contribute to nucleation behavior. Inverting high slip-rate and friction data from different types of experiments, we show that RSF can work by using parameter ranges far from typical low-velocity values. In comparison, we introduce "bristle-state" friction (BSF) models, developed by control-system engineers to predict the transient frictional evolution during arbitrary stressing, especially reversals through static conditions. Although BSF models were also designed for low-velocities, we show that their form provides advantages for fitting frictional evolution measurements under high slip-rate, long-displacement, non-trivial slip histories, especially during the initial strengthening stage.
Complex Crustal Deformation Controlled by the 3D Geometry of the Chile Subduction Zone
(2023) Herrera, Marco T.; Crempien, Jorge G. F.; Cembrano, Jose
The Chilean subduction zone hosts Mw > 8 earthquakes, which could trigger earthquakes on crustal faults located along the plate margin. Using synthetic earthquakes from a quasidynamic boundary element method model, we obtain traction fields and perform a slip tendency analysis to obtain synthetic faults, which we compare with existing potentially seismogenic crustal faults. With our results, we find geometric patterns of the highest slip tendency planes with deformations induced by synthetic subduction events, such that north of the rupture area of each event, correlate with normal N20(degrees)W-50(degrees)W/N60(degrees)SW fault planes, and to the south, correlate with normal N30(degrees)E-80(degrees)E/N60(degrees)NW faults planes. These observations agree with observed fault traces in central and northern Chile, and past observations of crustal fault reactivation.
Effects of earthquake spatial slip correlation on variability of tsunami potential energy and intensities
(2020) Crempien, Jorge G. F.; Urrutia, Alejandro; Benavente, Roberto; Cienfuegos, Rodrigo
Variability characterization of tsunami generation is quintessential for proper hazard estimation. For this purpose we isolate the variability which stems solely from earthquake spatial source complexity, by simulating tsunami inundation in the near-field with a simplified digital elevation model, using nonlinear shallow water equations. For earthquake rupture, we prescribe slip to have a log-normal probability distribution function and von Karman correlation between each subfault pair, which we assume decreases with increasing euclidean distance between them. From the generated near-field inundation time-series, emanating from several thousand synthetic slip realizations across a magnitude 9 earthquake, we extract several tsunami intensity measures at the coast. Results show that all considered tsunami intensity measures and potential energy variability increase with increasing spatial slip correlations. Finally, we show that larger spatial slip correlations produce higher tsunami intensity measure exceedance probabilities within the near-field, which highlights the need to quantify the uncertainty of earthquake spatial slip correlation.
Fractal Spatial Distributions of Initial Shear Stress and Frictional Properties on Faults and Their Impact on Dynamic Earthquake Rupture
(2024) Venegas-Aravena, Patricio; Crempien, Jorge G. F.; Archuleta, Ralph J.
We investigate the influence of the heterogeneous slip-weakening distance ( D-C ) in dynamic rupture simulations, in which D-C is proportional to the fault irregularities. Specifically, we compare a heterogeneous fractal D-C distribution to a uniform D-C over the entire fault when the initial shear stress is also heterogeneous. We find that even small changes in the average value of D-C ( < 1 mm) can lead to significant differences in the rupture evolution; that is, the average D-C and the way D(C )is distributed determines if the rupture is a runaway, self-arrested, or nonpropagating. We find that the self-arrested ruptures differ from runaway ruptures in the amount of area characterized by large slips (asperities). Self-arrested ruptures match the Somerville et al. (1999) asperity criteria in which - 25% of ruptured area radiate - 45% of the total seismic moment. This criterion is not satisfied for runaway ruptures. For runaway ruptures, - 50% of the ruptured area radiates about 70% of the seismic moment, indicating that the ruptured area is not linearly proportional to the seismic moment. Self-arrested ruptures are characterized by dynamic shear stress drops (SDs) in the range - 2.9 -5.5 MPa, whereas for runaway ruptures the dynamic SDs increase to values between -12 and 20 MPa. Self-arrested ruptures generated by fractal distributed D-C resemble the rupture properties of observed earthquakes. In addition, results show that the conditions for self-arrested ruptures are connected to the decrease of residual energy at rupture boundaries.
Multi-scale flow structure of a strike-slip tectonic setting: A self-similar model for the Liquine-Ofqui Fault System and the Andean Transverse Faults, Southern Andes (39-40 degrees S)
(PERGAMON-ELSEVIER SCIENCE LTD, 2022) Roquer, Tomas; Arancibia, Gloria; Crempien, Jorge G. F.; Mery, Domingo; Rowland, Julie; Sepulveda, Josefa; Veloso, Eugenio E.; Nehler, Mathias; Bracke, Rolf; Morata, Diego
The flow structure of a brittle crustal volume is defined by the multi-scale geometric and hydraulic properties of its fracture meshes. The length density distribution n(L,l) and the transmissivity distribution K(L,l) control the hydrologic scaling, where l is fracture length and L is the system size. The flow structure might display at most three key hydrologic scales: the connection scale, above which flow is focused in few critical paths; the channeling scale, above which flow is distributed in several paths; and the homogenization scale, above which permeability approaches a constant value. According to these scales, the hydrological structure could be distributed or clustered, thus having a clear impact in geothermal exploration campaigns and reservoir modeling. In this work, we determine the multi-scale flow structure for the Liquine-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF) in the Southern Andes, by establishing the hydrologic scaling they follow. Using fractal statistics, we integrated geological data at the regional, meso-and micro-scale, including image analysis from X-ray microtomography. Our results suggest a self-similar, dense network with n(L,l)similar to l(-a) and a = 2.6-2.9, from the regional scale where the LOFS and ATF interact to the meso-and micro-scale within highly fractured areas of the LOFS. Scaling models are constrained by the length distribution, and other power-law functions reflecting the geometric arrangement of fractures, as well as the spatial distribution of superficial geothermal occurrences. Thus, we expect the hydrologic scaling to depend on the transmissivity distribution. Lognormal transmissivity distribution yields a permeability increase with scale, from the connection to the homogenization scales; whereas power-law transmissivity distribution yields a permeability increase from the connection scale without a limiting value. Approximations of the connection scale are around 10(-3)-10(0) m; the channeling scale, around 100-104 m; and if the homogenization scale exists, it should be equal or greater than 10(3)-10(4) m. Finally, the results presented here could to define the internal architecture of fracture meshes in fault-controlled fluid flow, and be used to select an appropriate hydrologic model according to the analyzed scale. Therefore, these findings must be taken into consideration in future geothermal prospecting, modeling and exploitation.
Numerical modeling of the Nevados de Chillan fractured geothermal reservoir
(2025) Oyarzo-Cespedes, Isa; Arancibia, Gloria; Browning, John; Crempien, Jorge G. F.; Morata, Diego; Mura, Valentina; Lopez-Contreras, Camila; Maza, Santiago
Numerical models can be utilized to understand and anticipate the future behavior of a geothermal reservoir, and hence aid in the development of efficient reservoir engineering strategies. However, as each system has a unique geological context, individual characterization is required. In this research, the Nevados de Chillan Geothermal System (NChGS) in the Southern Volcanic Zone of the Andes is considered. The NChGS is controlled by the geology of the active Nevados de Chillan Volcanic Complex (NChVC) including their basement units (Miocene lavas and volcaniclastic layers from Cura-Mall & iacute;n Formation and the Miocene, Santa Gertrudis granitoids) as well as the key structural control from crustal scale faults, all of which combine to influence the reservoir characteristics. The presence of faults acts to generate a high secondary permeability which favors the circulation of hydrothermal fluids. Based on previous studies in the NChGS, we designed a thermo-hydraulic model in COMSOL Multiphysics (R) combining equations of heat transfer and Darcy's law in order to determine the distribution of isotherms and surface heat flux. The boundary conditions of the model were informed by a conceptual model of depth 3 km and width of 6.6 km which considers a highly fractured granitic reservoir, a clay cap behavior of Miocene lavas and volcaniclastic units, and transitional zones between a regional zone and the reservoir. A lowangle reverse fault affecting the clay cap unit was also incorporated into the models. Results indicate convective behavior in the reservoir zone and a surface heat flux of 0.102 W/m2 with a local peak up to 0.740 W/m2 in the area affected by the low-angle reverse fault zone. The models suggest hydrothermal fluid residence times of around 9-15 thousand years are required to reach a steady-state thermal configuration, which is consistent with the deglaciation age proposed for the NChVC latitude of the complex (c. 10-15 ka). Permeability in the fractured reservoir is one of the most complex parameters to estimate and the most sensitive and hence requires further constraint. Finally, using the volumetric method and the results obtained in this research, we estimate a geothermal potential of 39 +/- 1 MWe for the NChGS.
Recurrence time and size of Chilean earthquakes influenced by geological structure
(2024) Julve, Joaquin; Barbot, Sylvain; Moreno, Marcos; Tassara, Andres; Araya, Rodolfo; Catalan, Nicole; Crempien, Jorge G. F.; Becerra-Carreno, Valeria
In 1960, the giant Valdivia earthquake (moment magnitude, Mw, 9.5), the largest earthquake ever recorded, struck the Chilean subduction zone, rupturing the entire depth of the seismogenic zone and extending for 1,000 km along strike. The first sign of new seismic energy release since 1960 occurred in 2017 with the Melinka earthquake (Mw 7.6), which affected only a portion of the deepest part of the seismogenic zone. Despite the recognition that rupture characteristics and rheology vary with depth, the mechanical controls behind such variations of earthquake size remain elusive. Here we build quasi-dynamic simulations of the seismic cycle in southern Chile including frictional and viscoelastic properties, drawing upon a compilation of geological and geophysical insights to explain the recurrence times of recent, historic, and palaeoseismic earthquakes and the distribution of fault slip and crustal deformation associated with the Melinka and Valdivia earthquakes. We find that the frictional and rheological properties of the forearc, which are primarily controlled by the geological structure and fluid distribution at the megathrust, govern the magnitude and recurrence patterns of earthquakes in Chile.
Regional-scale seismic fragility, loss, and resilience assessment using physics-based simulated ground motions: An application to Istanbul
(2023) Zhang, Wenyang; Chen, Peng-Yu; Crempien, Jorge G. F.; Kurtulus, Asli; Arduino, Pedro; Taciroglu, Ertugrul
Using results from 57 large-scale physics-based fault-rupture and wave propagation simulations, this research aims to evaluate the seismic risk, loss, and resilience of more than 16,000 reinforced concrete buildings in the Zeytinburnu district of Istanbul, Turkey. For each building and under each earthquake scenario, the spatially varying site-specific simulated ground motions were used for performing three-dimensional nonlinear time-history analyses. The resulting structural responses-such as peak story drift ratios (PSDR) and peak floor accelerations (PFAs)-were utilized to conduct three region-scale tasks: (i) building- and site-specific seismic fragility analysis for both structural and nonstructural components of each building; (ii) intensity-based seismic loss assessment using the FEMA P58 methodology and Monte Carlo simulations; and (iii) resilience evaluation based on the expected time of recovery predicted through FEMA P58. Moreover, both inertial and kinematic soil-structure interaction (SSI) effects were considered using a substructuring method for all three tasks. Site-specific soil properties were utilized to compute the coefficients of soil springs and dashpots, as well as the foundation input motions. The SSI effects were investigated by comparing the fragility, loss, and resilience indices obtained with and without considering SSI.
Seismic cycle controlled by subduction geometry: novel 3-D quasi-dynamic model of Central Chile megathrust
(2024) Herrera, Marco T.; Crempien, Jorge G. F.; Cembrano, Jose; Moreno, Marcos
Subduction earthquakes show complex spatial and temporal rupture patterns, exhibiting events of varied sizes, which rupture distinct or overlapping fault segments. Elucidating first-order controlling conditions of rupture segmentation and return periods of large earthquakes is therefore critical for seismic and tsunami hazard estimations. The Chilean subduction zone frequently hosts several M-w > 8 earthquakes, with heterogeneous recurrence rates and locations. Here, we implement 3-D quasi-dynamic rate and state frictional models to investigate the role of plate interface geometry on the distribution of interseismic coupling and coseismic ruptures in Central Chile. First, we develop synthetic-parametric models that show how dip and strike variations may increase the probabilities to produce partial seismic barriers, which tend to avoid the production of large earthquake ruptures and modulate rupture lengths. Then, we simulate the subduction seismic cycle processes on Central Chile (25(degrees)S-38(degrees)S), imposing depth-dependent frictional properties on a realistic non-planar 3-D subduction interface geometry. Similar to results obtained for synthetic-parametric models, after 5000 yr of simulation, regions with abrupt dip or strike changes increase the probabilities of stopping coseismic propagation of simulated M-w 8.0-9.0 earthquakes. Our simulated earthquake sequences on the Central Chile subduction zone delimit rupture areas that match geometrical interface features and historical earthquakes, results that point to the crucial role of fault interface geometry on seismic cycle segmentation along strike.
ShakerMaker: A framework that simplifies the simulation of seismic ground-motions
(2022) Abell, Jose A.; Crempien, Jorge G. F.; Recabarren, Matias
ShakerMaker is an open-source python framework which simplifies the generation of synthetic broad-band seismograms, produced by finite-fault kinematic representations of earthquake ruptures, using a 1-D layered model of the crust and the frequency-wavenumber (f-k) method. It is designed to bring closer the engineering seismology and earthquake engineering communities, by catering to the earthquake simulation needs of both disciplines. One particular goal of this framework is to provide a simple way to produce high-fidelity earthquake motions for use with the domain-reduction method, simplifying the setup of physically accurate finite-element simulations of multi-scale seismological and earthquake engineering problems through the use of a new specialized file format.

Browsing by Author "Crempien, Jorge G. F."

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