Paul A. Johnson's research while affiliated with Los Alamos National Laboratory and other places

Publications (256)

Preprint
Characterizing fluid flow in a porous material with permeability is fundamental to energy and hydrological applications, yet direct measurements of permeability are very difficult to conduct in situ. However, attending fluid flow through a material are various mechanical responses, e.g., strain fields, acoustic emission. These mechanical responses...
Preprint
Full-text available
Machine learning models using seismic emissions can predict instantaneous fault characteristics such as displacement in laboratory experiments and slow slip in Earth. Here, we address whether the acoustic emission (AE) from laboratory experiments contains information about near-future frictional behavior. The approach uses a convolutional encoder-d...
Poster
Multiphase flow is common in fractures and flow paths associated with leaky wellbores, including liquid-phase (e.g., liquid forms of gas, crude oil) and gas-phase (e.g., gas ex-solved from liquid carbon dioxide, etc.). Upward leakage of any phase can contaminate sub-surface water-bearing formations, create hazardous surface conditions, and substant...
Article
Full-text available
Data-driven machine-learning for predicting instantaneous and future fault-slip in laboratory experiments has recently progressed markedly, primarily due to large training data sets. In Earth however, earthquake interevent times range from 10’s-100’s of years and geophysical data typically exist for only a portion of an earthquake cycle. Sparse dat...
Article
Full-text available
Systematically characterizing slip behaviours on active faults is key to unraveling the physics of tectonic faulting and the interplay between slow and fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling measurement of ground deformation at a global scale every few days, may hold the key to those interactions. However, a...
Article
Time Reversal and Nonlinear Elastic Wave Spectroscopy (TR-NEWS) has been used to focus acoustic energy, and make measurements correlated with damage in a variety of industrial materials. Most studies using TR-NEWS have focused on relatively small objects and may have multiple acoustic sources. In Earth, within energy extraction and carbon sequestra...
Article
Full-text available
Rocks under stress deform by creep mechanisms that include formation and slip on small‐scale internal cracks. Intragranular cracks and slip along grain contacts release energy as elastic waves termed acoustic emissions (AE). AEs are thought to contain predictive information that can be used for fault failure forecasting. Here, we present a method u...
Article
Full-text available
Mechanical stress acting in the Earth’s crust is a fundamental property that is important for a wide range of scientific and engineering applications. The orientation of maximum horizontal compressive stress can be estimated by inverting earthquake source mechanisms and measured directly from borehole-based measurements, but large regions of the co...
Article
Full-text available
Plain Language Summary Low frequency earthquakes (LFEs) are a class of events occurring deep in the fault core beneath the seismogenic zone. This type of event has been observed along the central San Andrea Fault and occurs much more frequently than regular earthquakes. This study applies gradient boosted tree models using statistical features deri...
Article
Full-text available
Plain Language Summary When intact materials are slightly squeezed or stretched, the amount of the material compresses or extends is typically some multiple of the applied force. Damaged materials have internal fractures, which makes this relationship more complicated. This is because fractures can be open or closed, each contributing differently t...
Preprint
Full-text available
Data-driven machine-learning for predicting instantaneous and future fault-slip in laboratory experiments has recently progressed markedly due to large training data sets. In Earth however, earthquake interevent times range from 10's-100's of years and geophysical data typically exist for only a portion of an earthquake cycle. Sparse data presents...
Preprint
The retrieval of earthquake finite-fault kinematic parameters after the occurrence of an earthquake is a crucial task in observational seismology. Routinely-used source inversion techniques are challenged by limited data coverage and computational effort, and are subject to a variety of assumptions and constraints that restrict the range of possibl...
Preprint
Full-text available
Time Reverse Nonlinear Elastic Wave Spectroscopy (TR-NEWS) has been used to focus acoustic energy, and make measurements correlated with damage in a variety of industrial materials. Most studies using TR-NEWS in Earth Science have focused on relatively small objects and may have multiple acoustic sources. In Earth, within energy extraction settings...
Article
We present experimental and modeling results and a downhole logging tool concept resulting from a research collaboration between Chevron Energy Technology Company and Los Alamos National Laboratory investigating using nonlinear acoustics applications for natural fracture characterization and assessing near-wellbore mechanical integrity or drilling-...
Article
The stress tensor is an important property for upper crustal studies such as those that involve pore fluids and earthquake hazards. At tectonic plate scale, plate boundary forces and mantle convection are the primary drivers of the stress field. In many local settings (10–100 s of km and <10 km depth) in tectonic plate interiors, we can simplify by...
Preprint
Full-text available
Mechanical stress acting in the Earth`s crust is a fundamental property that has a wide range of geophysical applications, from tectonic movements to energy production. The orientation of maximum horizontal compressive stress, S Hmax can be estimated by inverting earthquake source mechanisms and directly from borehole-based measurements, but large...
Article
Full-text available
Earthquake prediction, the long-sought holy grail of earthquake science, continues to confound Earth scientists. Could we make advances by crowdsourcing, drawing from the vast knowledge and creativity of the machine learning (ML) community? We used Google’s ML competition platform, Kaggle, to engage the worldwide ML community with a competition to...
Preprint
Full-text available
Systematic characterization of slip behaviours on active faults is key to unraveling the physics of tectonic faulting and the interplay between slow and fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling measurement of ground deformation at a global scale every few days, may hold the key to those interactions. However,...
Preprint
Full-text available
Active faults release tectonic stress imposed by plate motion through a spectrum of slip modes, from slow, aseismic slip, to dynamic, seismic events. Slow earthquakes are often associated with tectonic tremor, non-impulsive signals that can easily be buried in seismic noise and go undetected. We present a new methodology aimed at improving the dete...
Article
A new cross-journal special collection invites contributions on how machine learning can be used for solid Earth observation, modeling and understanding.
Article
Full-text available
Laboratory earthquake experiments provide important observational constraints for our understanding of earthquake physics. Here we leverage continuous waveform data from a network of piezoceramic sensors to study the spatial and temporal evolution of microslip activity during a shear experiment with synthetic fault gouge. We combine machine learnin...
Article
Full-text available
Slow slip events result from the spontaneous weakening of the subduction megathrust and bear strong resemblance to earthquakes, only slower. This resemblance allows us to study fundamental aspects of nucleation that remain elusive for classic, fast earthquakes. We rely on machine learning algorithms to infer slow slip timing from statistics of seis...
Preprint
Geophysics has historically been a data-driven field, however in recent years the exponential increase of available data has lead to increased adoption of machine learning techniques and algorithm for analysis, detection and forecasting applications to faulting. This work reviews recent advances in the application of machine learning in the study o...
Preprint
Full-text available
Geophysics has historically been a data-driven field, however in recent years the exponential increase of available data has lead to increased adoption of machine learning techniques and algorithm for analysis, detection and forecasting applications to faulting. This work reviews recent advances in the application of machine learning in the study o...
Article
Full-text available
Slow earthquakes may trigger failure on neighboring locked faults that are stressed sufficiently to break, and slow slip patterns may evolve before a nearby great earthquake. However, even in the clearest cases such as Cascadia, slow earthquakes and associated tremor have only been observed in intermittent and discrete bursts. By training a convolu...
Article
Full-text available
While the rupture processes of nearby earthquakes are often highly similar, characterizing the differences can provide insight into the complexity of the stress field and fault network in which the earthquakes occur. Here we perform a comprehensive analysis of earthquake waveform similarity to characterize rupture processes in the vicinity of Ridge...
Chapter
Full-text available
Geophysics has historically been a data-driven field. In recent years, the intersection of exponentially increasing amounts of data and cheap computing power, from graphics cards in particular, has led to an increasing adoption of machine learning and deep learning techniques, in geoscience in general, and fault physics in particular. This work rev...
Preprint
When a rock is subjected to stress it deforms by creep mechanisms that include formation and slip on small-scale internal cracks. Intragranular cracks and slip along grain contacts release energy as elastic waves called acoustic emissions (AE). Early research into AEs envisioned that these signals could be used in the future to predict rock falls,...
Article
The association of seismic‐wave arrivals with causative earthquakes becomes progressively more challenging as arrival detection methods become more sensitive, and particularly when earthquake rates are high. For instance, seismic waves arriving across a monitoring network from several sources may overlap in time, false arrivals may be detected, and...
Preprint
Full-text available
Plate motion near the fault gouge layer, and the elastic interplay between the gouge layer and the plate under stick-slip conditions, is key to understanding the dynamics of sheared granular fault systems. Here, a two-dimensional implementation of the combined finite-discrete element method (FDEM), which merges the finite element method (FEM) and t...
Article
This paper presents an analytical model that describes the relationship between interface stiffness and separation of rough interfaces such as fatigue cracks. The contact acoustic nonlinearity at the interface is simulated by a quasi-static model based on Hertzian contact theory. The model is validated using the results of dynamic acoustoelastic te...
Preprint
Full-text available
Volcanic tremor is key to our understanding of active magmatic systems but, due to its complexity, there is still a debate concerning its origins and how it can be used to characterize eruptive dynamics. In this study we leverage machine learning (ML) techniques using 6 years of continuous seismic data from the Piton de la Fournaise volcano (La Réu...
Preprint
We report on slow earthquakes in Northern Cascadia, and show that continuous seismic energy in the subduction zone follows specific patterns leading to failure. We rely on machine learning models to map characteristic energy signals from low-amplitude seismic waves to the timing of slow slip events. We find that patterns in seismic energy follow th...
Article
A numerical scheme using the combined finite-discrete element method is employed to study a model of an earthquake system comprising a granular layer embedded in a formation. When the formation is driven so as to shear the granular layer, a system of stress chains emerges. The stress chains endow the layer with resistance to shear and on failure la...
Conference Paper
Source ground vibration in fault blocks of granular fault with respect to stick-slips is important to understand the dynamic behavior of sheared granular fault system. Here, a two-dimensional implementation of the combined finite-discrete element method (FDEM), which merges the finite element method (FEM) and the discrete element method (DEM), is u...
Preprint
Slow earthquakes and associated tremor are common to most subduction zones, taking place down dip from the neighboring locked zone where megathrust earthquakes occur. We report observation of quasi-continuous tremor that quantifies the slow slip rate at all times. By training a convolutional neural network to detect known tremor on a single station...
Article
Numerical simulation of nonlinear elastic wave propagation in solids with cracks is indispensable for decoding the complicated mechanisms associated with the nonlinear ultrasonic techniques in Non-Destructive Testing (NDT). Here, we introduce a two-dimensional implementation of the combined finite-discrete element method (FDEM), which merges the fi...
Article
Full-text available
2nd Annual Machine Learning in Solid Earth Geoscience Conference; Santa Fe, New Mexico, 18–22 March 2019
Poster
Full-text available
Elastic properties of materials change when subjected to an external excitation, causing either transitory or permanent variations in their dynamic response. In buildings, fundamental frequencies show a rapid decrease with loading, followed by a recovery over time that is dependent on the level of damage produced by the excitation. This is due to a...
Poster
High-frequency (HF) seismic radiation is associated with abrupt changes of rupture velocity and slip-rate during earthquake faulting. Many studies have attempted to illuminate rupture heterogeneities of large earthquakes through the use of coherent imaging techniques such as the back-projection (BP) [e.g. Satriano et al. (2014), Lay et al. (2012)]....
Preprint
Full-text available
The association of seismic wave arrivals with causative earthquakes becomes progressively more challenging as arrival detection methods become more sensitive, and particularly when earthquake rates are high. For instance, seismic waves arriving across a monitoring network from several sources may overlap in time, false arrivals may be detected, and...
Article
Understanding the behavior of Earth through the diverse fields of the solid Earth geosciences is an increasingly important task. It is made challenging by the complex, interacting, and multiscale processes needed to understand Earth’s behavior and by the inaccessibility of nearly all of Earth’s subsurface to direct observation. Substantial increase...
Preprint
The seismogenic plate boundaries are presumed to behave similarly to a densely packed granular medium, where fault and blocks systems rapidly rearrange the distribution of forces within themselves, as particles do in slowly sheared granular systems. We use machine learning and show that statistical features of velocity signals from individual parti...
Article
Many geological materials, ranging from “rocks to unconsolidated sand,” exhibit highly nonlinear elastic properties. Rocks fall in to a class of materials know as Nonlinear Mesoscopic Elastic Mesoscopic materials (NMEMs) in which the nonlinearity they possess is not derived from the constituent material, but rather the microscopic structure. Their...
Preprint
Full-text available
A numerical scheme using the combined finite-discrete element methods (FDEM) is employed to study a model of an earthquake system comprising a granular layer embedded in a formation. When the formation is driven so as to shear the granular layer, a system of stress chains emerges. The stress chains endow the layer with resistance to shear and on fa...
Preprint
A numerical scheme using the combined finite-discrete element methods (FDEM) is employed to study a model of an earthquake system comprising a granular layer embedded in a formation. When the formation is driven so as to shear the granular layer, a system of stress chains emerges. The stress chains endow the layer with resistance to shear and on fa...
Article
Full-text available
We present an approach based on machine learning (ML) to distinguish eruption and precursory signals of Chimayó geyser (New Mexico, U.S.A.) under noisy environmental conditions. This geyser can be considered a natural analog of CO 2 intrusion into shallow water aquifers. By studying this geyser, we can understand upwelling of CO 2 -rich fluids from...
Article
Correctly determining the association of seismic phases across a network is crucial for developing accurate earthquake catalogs. Nearly all established methods use travel time information as the main criterion for determining associations, and in problems in which earthquake rates are high and many false arrivals are present, many standard techniqu...
Article
Full-text available
Elastic properties of civil engineering structures change when subjected to a dynamic excitation. The modal frequencies show a rapid decrease followed by a relaxation, or slow recovery, that is dependent on the level of damage. In this article, we analyze the slow recovery process applying three relaxation models to fit real earthquake data recorde...
Chapter
The term nonlinear resonant ultrasound spectroscopy (NRUS) was first coined in the 1990s and is one of the earliest nonlinear techniques used to quantify global damage in a sample. This chapter was written as an introduction and overview for the general reader, one interested in learning more about the technique, especially its origins. As rocks ar...
Article
Full-text available
Tectonic faults fail in a spectrum of modes, ranging from earthquakes to slow slip events. The physics of fast earthquakes are well described by stick–slip friction and elastodynamic rupture; however, slow earthquakes are poorly understood. Key questions remain about how ruptures propagate quasi-dynamically, whether they obey different scaling laws...
Article
Full-text available
Tectonic faults slip in various manners, which range from ordinary earthquakes to slow slip events to aseismic fault creep. Slow slip and associated tremor are common to many subduction zones, and occur down-dip from the neighbouring locked zone where megaquakes take place. In the clearest cases, such as Cascadia, identified tremor occurs in discre...
Article
Machine learning regression can predict macroscopic fault properties such as shear stress, friction, and time to failure using continuous records of fault zone acoustic emissions. Here we show that a similar approach is successful using event catalogs derived from the continuous data. Our methods are applicable to catalogs of arbitrary scale and ma...