Brendan J Meade

Harvard University | Harvard · Department of Earth and Planetary Sciences

Fault slip during the earthquake cycle is often spatially heterogeneous and occurs on non-planar fault surfaces. In this study, we present an analytical method for calculating displacements and stresses resulting from spatially variable fault slip on faults with arbitrary geometry in a linear elastic medium. This method enforces that fault slip is...

We describe an implementation of an analytic approach to calculating displacements and stresses resulting from fault slip in a linear elastic medium. This approach is based on the idea that fault slip is both spatially continuous and smoothly differentiable to first-order. Compared with the classical constant-slip Green's function boundary element...

Non‐inertial afterslip has been inferred to occur following large earthquakes. An explanation for this slow slip phenomenon is that coseismically generated stresses induce sliding on parts of a fault surface with velocity‐strengthening frictional properties. Here we develop an alternative mesoscale heuristic explanation for afterslip based on the i...

Non-inertial afterslip has been inferred to occur following large earthquakes. An explanation for this slow slip phenomenon is that coseismically generated stresses induce sliding on parts of a fault surface with velocity-strengthening frictional properties. Here we develop an alternative explanation for afterslip based on the idea that afterslip m...

Forecasting the timing of earthquakes is a long-standing challenge. Moreover, it is still debated how to formulate this problem in a useful manner, or to compare the predictive power of different models. Here, we develop a versatile neural encoder of earthquake catalogs, and apply it to the fundamental problem of earthquake rate prediction, in the...

Computational earthquake sequence models provide generative estimates of the time, location, and size of synthetic seismic events that can be compared with observed earthquake histories and assessed as rupture forecasts. Here we describe a three-dimensional probabilistic earthquake sequence model that produces slip event time series constrained acr...

Viscoelastic processes in the upper mantle redistribute seismically generated stresses and modulate crustal deformation throughout the earthquake cycle. Geodetic observations of these motions at the surface of the crust‐mantle system offer the possibility of constraining the rheology of the upper mantle. Parsimonious representations of viscoelastic...

Viscoelastic deformation below the Earth’s elastic crust is modulated by stresses generated by both plate tectonic and earthquake cycle processes. Rapid near-fault deformation following large earthquakes has been interpreted as the signature of viscoelastic stress diffusion in the upper mantle and earthquake cycle models have been developed that in...

Interseismic geodetic observations at active boundaries contain information about tectonic motions and earthquake cycle processes. The combined effects of these two processes may serve to mask tectonic signals near active faults. Motivated by the observation of coseismic rotational motion during the 2016 Mw 7.8 Kaikōura New Zealand earthquake we de...

Viscoelastic processes in the upper mantle redistribute seismically generated stresses and modulate crustal deformation throughout the earthquake cycle. Geodetic observations of these motions at the Earth's surface offer the possibility of constraining the rheology of the upper mantle. Parsimonious representations of viscoelastically modulated defo...

The past 100 years have seen the occurrence of five MW≥9 earthquakes and 94 MW≥8 earthquakes. Here we assess the potential for future great earthquakes using inferences of interseismic subduction zone coupling from a global block model incorporating both tectonic plate motions and earthquake cycle effects. Interseismic earthquake cycle effects are...

Linear elastic boundary element models are commonly used tools to understand the mechanics of earthquake cycle processes and their contribution to the growth of tectonic structures. Here we describe a two-dimensional plane strain linear elastic boundary element approach to earthquake cycle and tectonic processes based on the displacement discontinu...

The past 100 years have seen the occurrence of five $\MW\geq9$ earthquakes and 94 $\MW\geq8$ earthquakes. Here we assess the potential for future great earthquakes using inferences of interseismic subduction zone coupling from a global block model incorporating both tectonic plate motions and earthquake cycle effects. Interseismic earthquake cycle...

The Cascadia subduction zone hosts great $\mathrm{M}_\mathrm{W} > 8.5$ earthquakes, but studying these events is hindered by our short observational record. Earthquake cycle simulation provides an alternative window into the behavior of the subduction zone. Here, we present simulations over 3,800 years, 14 ruptures and hundreds of slow slip events...

Boundary element methods have become a foundational tool in earthquake science for the modeling of earthquake cycle kinematics. Despite their wide use and convenience typical rectangular and triangular constant slip dislocation methods produce stress singularities at the edges of every element rendering these models physically unrealistic. As we de...

This article provides an overview of current applications of machine learning (ML) in seismology. ML techniques are becoming increasingly widespread in seismology, with applications ranging from identifying unseen signals and patterns to extracting features that might improve our physical understanding. The survey of the applications in seismology...

Aftershocks are a response to changes in stress generated by large earthquakes and represent the most common observations of the triggering of earthquakes. The maximum magnitude of aftershocks and their temporal decay are well described by empirical laws (such as Bath’s law¹ and Omori’s law²), but explaining and forecasting the spatial distribution...

The rotations of tectonic plates provide a partial description of the total observed displacements at the Earth's surface. The estimated number of kinematically distinct plates has increased from 12 in 1990 to 56 in 2010 as a result of the increase in the number of kinematic observables. At length scales <1,000 km, rotation-only plate models are in...

Images of earthquake slip serve as the foundation for understanding the distribution of coseismic energy release, theories about rupture propagation, and fault mechanics. Geodetic slip images are inferred using elastic models that link surface observations to fault activity at depth. To date, almost all elastic models used for these common calculat...

Comparison of pre-event geodetic and geologic rates in three large-magnitude (Mw=7.6-7.9) strike-slip earthquakes reveals a wide range of behaviors. Specifically, geodetic rates of 26-28 mm/yr for the North Anatolian fault along the 1999 MW=7.6 Izmit rupture are ∼40% faster than Holocene geologic rates. In contrast, geodetic rates of ∼6-8 mm/yr alo...

Aftershocks may be triggered by the stresses generated by preceding mainshocks. The temporal frequency and maximum size of aftershocks are well described by the empirical Omori and Bath laws, but spatial patterns are more difficult to forecast. Coulomb failure stress is perhaps the most common criterion invoked to explain spatial distributions of a...

Earthquakes at seismogenic plate boundaries are a response to the differential motions of tectonic blocks embedded within a geometrically complex network of branching and coalescing faults. Elastic strain is accumulated at a slow strain rate of the order of $10^{-15}$ s$^{-1}$, and released intermittently at intervals $>100$ years, in the form of r...

Plate motions are governed by equilibrium between basal and edge forces. Great earthquakes may induce differential static stress changes across tectonic plates, enabling a new equilibrium state. Here we consider the torque balance for idealized circular plates and find a simple scalar relationship for changes in relative plate speed as a function o...

One of the most significant challenges involved in efforts to understand the effects of repeated earthquake cycle activity are the computational costs of large-scale viscoelastic earthquake cycle models. Computationally intensive viscoelastic codes must be evaluated thousands of times and locations, and as a result, studies tend to adopt a few fixe...

Along the North Anatolian fault (NAF), the surface deformation associated with tectonic block motions, elastic strain accumulation, and the viscoelastic response to past earthquakes has been geodetically observed over the last two decades. These observations include campaign-mode Global Positioning System (GPS) velocities from the decade prior to t...

Over the past 80 years, 8 MW > 6.7 strike-slip earthquakes west of 40° longitude have ruptured the North Anatolian fault (NAF) from east to west. The series began with the 1939 Erzincan earthquake in eastern Turkey, and the most recent 1999 MW = 7.4 Izmit earthquake extended the pattern of ruptures into the Sea of Marmara in western Turkey. The mea...

Following large earthquakes, coseismic stresses at the base of the seismogenic zone may induce rapid viscoelastic deformation in the lower crust and upper mantle. As stresses diffuse away from the primary slip surface in these lower layers, the magnitudes of stress at distant locations (>1 fault length away) may slowly increase. This stress relaxat...

Spatial patterns of interplate coupling on global subduction zones can be used to guide seismic hazard assessment, but estimates of coupling are often constrained using a limited temporal range of geodetic data. Here we analyze ~19 years of geodetic observations from the GEONET network to assess time-dependent variations in the spatial distribution...

Global Navigation Satellite System (GNSS) position time series are used pervasively in earthquake science to measure the surface response to earthquake cycle deformation. Characteristic usage cases are focused on the temporal windowing of position data to isolate coseismic, postseismic, or interseismic deformation. Here, we present an interactive v...

SUMMARY Geodetic observations of interseismic deformation in the Western United States provide constraints on microplate rotations, earthquake cycle processes, and slip partitioning across the Pacific–North America Plate boundary. These measurements may be interpreted using block models, in which the upper crust is divided into microplates bounded...

The Longmen Shan is the steepest topographic front at the India-Asia collision zone and the site of the Mw 7.9 Wenchuan earthquake. Here, to explain the interseismic GPS velocities across the greater Longmen Shan region, we develop a boundary element model including earthquake cycle effects, topography, the westward dipping Beichuan fault, and a ~2...

Online Material: Figures showing potential areas and magnitudes of earthquakes rupturing partially coupled regions of the subduction zones. In the wake of the 2011 great Tohoku‐Oki, Japan, earthquake, questions were asked about the extent to which this earthquake ruptured a part of the subduction zone that had been strongly coupled in the decades...

Characterizing surface deformation throughout a full earthquake cycle is a challenge due to the lack of high-resolution geodetic observations of duration comparable to that of characteristic earthquake recurrence intervals (250-10,000 years). Here we approach this problem by comparing long-term geologic slip rates with geodetically derived fault sl...

[1] The India-Asia collision zone accommodates the relative motion between India and Eurasia through both shortening and pervasive strike-slip faulting. To gain a mechanical understanding of how fault slip rates are driven across the Tibetan plateau, we develop a two-dimensional, linear elastic, two-stage, deformable microplate model for the upper...

[1] Geodetic observations of interseismic deformation across the Tibetan plateau contain information about both tectonic and earthquake cycle processes. Time-variations in surface velocities between large earthquakes are sensitive to the rheological structure of the subseismogenic crust, and, in particular, the viscosity of the middle and lower cru...

Orogens at convergent margins must meet the energetic requirements necessary to lift rocks against gravity, allow for frictional sliding along basal detachments and accommodate internal deformation processes. The combination of critical taper and kinematic wedge theories predicts the partitioning between these energy sinks as a function of both fau...

Geodetic observations of surface displacements during and following earthquakes such as the March 11, 2011 great Tohoku earthquake can be used to constrain the spatial extent of coseismic slip and postseismic afterslip, and characterize the spectrum of earthquake cycle behaviors. Slip models are often regularized by assuming that slip on the fault...

The Hayward fault in the San Francisco Bay Area (SFBA) is sometimes considered unusual among continental faults for exhibiting significant aseismic creep during the interseismic phase of the seismic cycle while also generating sufficient elastic strain to produce major earthquakes. Imaging the spatial variation in interseismic fault creep on the Ha...

Understanding the relationship between strain accumulation and release in subduction zones is limited by our ability to resolve and compare spatial patterns of coseismic slip and interseismic slip deficit. In earthquake geodesy, estimates of fault slip are traditionally determined by regularized least squares minimization. Implicit in this approach...

Models of earthquake cycle behavior are typically predicated on the assumption that fault slip rates are known. The geologic and geodetic characterization of fault slip rates has progressed rapidly while the question of why faults slip at current rates remains poorly understood. Here we introduce an elastic, quasi-static, boundary-tracking finite e...

Over the past twenty-five years there has been significant debate about the kinematics and dynamics of deformation at continental plate boundaries, and, in particular, at the India-Asia collision zone. To understand slip partitioning and fault system evolution in this region, we have developed a quasi-static finite element model that combines both...

Geodetic observations of deformation across the Tibetan plateau contain information about both tectonic and earthquake cycle processes. Time-dependent variations in surface velocities may occur as a result of stress relaxation in a weak lower crustal channel underneath the plateau. Earthquake cycle models with a weak lower crustal channel reveal su...

During the interseismic phase of the earthquake cycle, between large earthquakes, stress on faults evolves in response to elastic strain accumulation driven by tectonic plate motions. Because earthquake cycle processes induce non-local stress changes, the interseismic stress accumulation rate on one fault is influenced by the behavior of all nearby...

Imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre-seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle. Both geodetic and seismic estimates of the coseismic rupture extent for the March 11, 2011 MW = 8.9-9.0 earthquake Tohoku-ok...

The spatial complexity of continental deformation in the greater Tibetan Plateau region can be defined as the extent to which relative motion of the Indian and Asian plates is partitioned between localized slip on major faults and distributed deformation. Potency rates provide a quantitative metric for determining the magnitudes of diffuse and on-f...

Discrepancy between slip rates derived geodetically and from geological measurements has often been claimed to be the rule rather than the exception. In some cases, the differences can reach more than 100% between values published for the same fault. Theses differences remain the subject of strong arguments between the communities involved, each co...

Comparisons of geologic slip rates from the North Anatolian fault (NAF) with slip rate estimates inferred from block models constrained by pre-1999 GPS velocities reveal that the geologic rates are consistently slower than the geodetic rates. This discrepancy characterizes the central and western NAF but is most pronounced in the structurally compl...

Over the past twenty-five years there has been significant debate about the kinematics and dynamics of upper crustal deformation at continental plate boundaries, and, in particular, at the India-Asia collision zone. To understand slip partitioning and fault system evolution across the greater Tibet region, we simulate the collision using a combined...

The spatial complexity of continental deformation in the greater Tibetan Plateau region can be defined as the extent to which relative motion of the Indian and Asian plates is partitioned between localized slip on major faults and distributed deformation processes. Potency rates provide a quantitative metric for determining the magnitudes of on-fau...

Fault systems at active plate boundaries accommodate the differential motion of tectonic plates through slip on anastomosing faults within the seismogenic upper crust. The partitioning of slip across fault systems can be inferred from models of space-based geodetic measurements to estimate both fault slip rates and interseismic fault creep. Covaria...

Fifty percent of the relative motion between the Indian and Asian plates is accommodated by active convergence at the Himalayan Range Front (HRF). Earthquake cycle processes on shallowly dipping HRF thrust faults generate large earthquakes (M-W >= 7) and contribute to the growth of HRF topography. Interseismic rock uplift rates reach a maximum nort...

Earth and Planetary Sciences Interseismic deformation in Japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces. We use spherical linear block theory constrained by geodetic observations...

Interseismic GPS measurements from the greater Tibetan plateau region demonstrate that the relative motion between the Indian and Eurasian plates is partitioned across a boundary exceeding 1000 km in width. These geodetic observations have been used to argue that continental deformation may be described as ``diffuse'' or ``plate-like'', two apparen...

We seek to quantify the relationship between interseismic slip activity and microseismicity along the Hayward fault in the eastern San Francisco Bay Area. During the interseismic regime the Hayward fault is known to exhibit variable degrees of locking both along strike and down-dip. Background microseismicity on and near the fault has been suggeste...

Rates of deformation at plate boundary zones are most commonly quantified using fault slip rates. Geologic fault slip rate estimates are constrained by dated offset marker units while geodetic fault slip rate estimates are based on model based inferences from interseismic velocity gradients. We present a new compilation of geologic and geodetic sli...

In southern Caliornia, the relative motion between the Pacific and North American plates is accommodated across a ~200 km wide fault system. We simultaneously estimate micro-plate rotations, fault slip rates, elastic strain accumulation rates, and spatially variable coupling on fault surfaces using a block model, based on the SCEC rectilinear Commu...

The Mw=7.5 1999 Izmit earthquake ruptured a western section of the North Anatolian fault system in Turkey. Surface deformation recorded by GPS stations both before and after the Izmit earthquake provides a glimpse into the rheology of the ductile lithosphere and reveals that the bulk viscosity of the lithosphere varies over the seismic cycle. On th...

Earth and Planetary Sciences Geodetic observations of interseismic deformation provide constraints on the partitioning of fault slip across plate boundary zones, the spatial distribution of both elastic and inelastic strain accumulation, and the nature of the fault system evolution. Here we describe linear block theory, which decomposes surface vel...

Geodetic data from the Global Navigation Satellite System (GNSS), and from satellite interferometric radar (InSAR) are revolutionizing how we look at instantaneous tectonic deformation, but the significance for long-term finite strain in orogenic belts is less clear. We review two different ways of analyzing geodetic data: velocity gradient fields...

Elastic dislocation models of geodetic measurements above subduction zones have led to the identification of MW ≈ 6.0–7.2 slow slip events (SSEs) that release elastic strain over periods of days to months, but great (MW ≥ 8) SSEs have remained unidentified. We extrapolate observations of SSE duration and slip magnitude to show that slip velocity de...

The San Francisco Bay Area has not experienced a major earthquake beneath and urban center since 1906. The Hayward fault is the most populated fault in the area, and 140 years after its last rupture, also has the greatest risk associated with it. A contiguous subsurface stepover connecting the Hayward and the Calaveras faults appears to directly tr...

Deformation of both subducting and overriding at convergent plate boundaries tends to dissipate energy that would otherwise be used to drive plate motions. For subducting plates, the magnitude of the bending deformation is not known because of poor constraints on slab strength. For overriding plates, back-arc orogeny results from upper plate shorte...

The Japanese Islands mark the leading edge of the Pacific-greater Eurasia plate boundary zone, where deformation is partitioned between upper plate faults and subduction zones. We use a three-dimensional spherical block model, constrained by the spatially dense Geonet GPS network, to simultaneously estimate plate motions, fault slip rates, and spat...

Present-day orography at the Andean margin is a result of isostasy, tectonic accretion, and erosional processes. The resulting excess mass of the Andes gives rise to frictional stresses on the seismogenic plate interface that resist the sinking of the subducting slab into the upper mantle. Thus, subduction rates should be sensitive to the time-depe...

Analog and numerical models predict a coupling between climate and tectonics whereby erosion infl uences the deformation of orogens. A testable prediction from modeling studies is the decrease in width of mountain ranges as a result of increased precipitation. Here we evaluate the effect of climate on a critically tapered orogen, the central Andes,...

To constrain the spatial distribution of erosion rates in the Waimea river watershed, on the western side of the island of Kauai, Hawaii, we calculate the frequency distribution of cosmogenic 3He concentrations ([3He]c) from helium isotopic measurements in olivine grains from a single sample of river sediment. Helium measurements were made in 26 al...

The spatial partitioning of deformation in the continental crust and, in particular, at plate boundary zones is determined by the distribution of fault slip-rates. Analytic and numerical models of strain accumulation in the elastic upper crust have been divided into those that parameterize faulting as localized on a finite length fault system compr...

The spatial partitioning of deformation in the continental crust and, in particular, at plate boundary zones is determined by the distribution of fault slip-rates. Analytic and numerical models of strain accumulation in the elastic upper crust have been divided into those that parameterize faulting as localized on a finite length fault system compr...

We present algorithms for analytically calculating the displacements, strains, and stresses associated with slip on a triangular dislocation element (TDE) in a homogeneous elastic half space. Following previous efforts, the solution is constructed as a dislocation loop where the deformation fields for each of the three triangle legs are calculated...

The collision of the Indian subcontinent with Asia drives the growth and evolution of the greater Tibetan Plateau region. Fault slip rates resulting from the relative motion between crustal blocks can provide a kinematic description of the distribution of present-day deformation. I construct a three-dimensional, regional-scale elastic block model o...

The collision of the Indian subcontinent with Asia drives the growth and evolution of the greater Tibetan plateau region. Fault slip rates resulting from the relative motion between crustal blocks can provide a kinematic description of the distribution present day deformation. We construct a three-dimensional, regional-scale elastic block model of...

To constrain the spatial distribution of erosion rates in a drainage basin we constructed a frequency distribution of cosmogenic 3He concentrations (3Hec) from helium isotopic measurements in olivine grains from a single sample of river sediment. The sediment sample is from the Waimea River, on the western side of the island of Kauai, Hawaii. Heliu...

Despite much progress, many questions remain regarding the potential dynamic coupling between atmospheric and lithospheric processes in the long-term evolution of mountain belts. As a complement to recent efforts to discover the interrelationships among climate, topography, erosion, and rock deformation under conditions of mass-flux steady state, w...

Over the last several years quantitative models have been developed to predict the steady state form of mountain belts. These models define steady state in terms of mass conservation, where climate mediated erosional efflux is balanced by tectonic influx. However, paleoclimate records suggest that climate is not steady and varies over a wide range...

The balance between interseismic elastic strain accumulation and coseismic release defines the extent to which a fault system exhibits a surplus or deficit of large earthquakes. We calculate the regional moment accumulation rate in southern California based on a fault slip rate catalog estimated from a block model of interseismic deformation constr...

We estimate slip rates on major active faults in southern California using a block model constrained by Global Positioning System measurements of interseismic deformation. The block model includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle. Our estimates of the right-lateral...

The clustering of earthquakes in time on the same fault affects the rate and pattern of interseismic deformation. We develop a simple analytic viscoelastic model of the surface velocity field through a clustered earthquake cycle by superposing the velocities of individual earthquake cycles of constant period but varying phase. Velocity profiles pri...

Many important insights regarding the coupling among climate, erosion, and tectonics have come from numerical simulations using coupled tectonic and surface process models. However, analyses to date have left the strength of the coupling between climate and tectonics uncertain and many questions unanswered. We present an approximate analytical solu...

We present a novel method for detecting regions of seismic moment deficit. These are areas where the moment release associated with large historical earthquakes does not balance the moment accumulation rate observed today. The total deformation field for the last two centuries is calculated by converting estimated focal mechanisms to rupture length...

We estimate present day slip rates on all of the major faults in southern California using block models fit to the geodetically determined interseismic velocities of the SCEC Crustal Motion Model (http://www.scec.org). The block model approach accounts for elastic strain accumulation due to motion on block-bounding faults and yields kinematically c...

The recognition of a dynamic coupling among climate, erosion and tectonics is arguably one of the most exciting discoveries in the last 20 years. Numerical simulations using coupled thermo-mechanical and surface process models have been most influential. However, analyses to date leave the strength of the coupling between climate and tectonics unce...

We model the geodetically observed secular velocity field in northwestern Turkey with a block model that accounts for recoverable elastic-strain accumulation. The block model allows us to estimate internally consistent fault slip rates and locking depths. The northern strand of the North Anatolian fault zone (NAFZ) carries approximately four times...

We use Global Positioning System (GPS) data from 1993–2000 to determine horizontal velocities of 65 stations in eastern California and western Nevada between 35° and 37° N. We relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the ef...

We interpret Global Positioning System measurements of interseismic deformation throughout the western Tien Shan in the context of a block model which accounts for important geologic features (faults) and physical processes (elastic strain accumulation.) Through this analysis we are able to quantify the amount of deformation localized on active str...