Joern Davidsen

The University of Calgary | HBI · Department of Physics and Astronomy

We utilize a model of Wilson-Cowan oscillators to investigate structure-function relationships in the human brain by means of simulations of the spontaneous dynamics of brain networks generated through human connectome data. This allows us to establish relationships between the global excitability of such networks and global structural network quan...

We investigate induced seismicity associated with a hydraulic stimulation campaign performed in 2020 in the 5.8 km deep geothermal OTN‐2 well near Helsinki, Finland as part of the St1 Deep Heat project. A total of 2,875 m³ of fresh water was injected during 16 days at well‐head pressures <70 MPa and with flow rates between 400 and 1,000 L/min. The...

Family law in many countries has changed radically since the 1960s. However, despite family law’s central importance, few detailed quantitative analyses of the relationship between legal developments (landmark judgments and statutory changes) and the amount and subject of family litigation have been made. We examine this relationship using a unique...

Fully and partially synchronized brain activity plays a key role in normal cognition and in some neurological disorders, such as epilepsy. However, the mechanism by which synchrony and asynchrony co-exist in a population of neurons remains elusive. Chimera states, where synchrony and asynchrony coexist, have been documented only for precisely speci...

Previous studies of injection-induced earthquake sequences have shown that the maximum magnitude (Mmax) of injection-induced seismicity increases with the net injected volume (V); however, different proposed seismic-hazard paradigms predict significantly different values of Mmax. Using injection and seismicity data from two project areas in northea...

Induced seismicity has become a concern for industry and nearby residents. Fluid-induced earthquakes are a side effect of industrial operations such as hydraulic fracturing, where high-pressure fluids are pumped into the Earth’s crust to increase hydrocarbon flow to a well from petroleum-bearing rock formations. Previous studies on fluid-induced se...

Plain Language Summary Fluid‐induced earthquakes are a side effect of industrial operations such as hydraulic fracturing and enhanced geothermal systems, where high‐pressure fluids are pumped into the earth's crust to increase oil and/or gas flow to a well from petroleum‐bearing rock formations or to improve permeability in underground geothermal r...

The frictional instability associated with earthquake initiation and earthquake dynamics is believed to be mainly controlled by the dynamics of fragmented rocks within the fault gauge. Principal features of the emerging seismicity (e.g., intermittent dynamics and broad time and/or energy scales) have been replicated by simple experimental setups, w...

Observations of neurons in a resting brain and neurons in cultures often display spontaneous scale-free collective dynamics in the form of information cascades, also called “neuronal avalanches”. This has motivated the so called critical brain hypothesis which posits that the brain is self-tuned to a critical point or regime, separating exponential...

Aftershock cascades are a characteristic feature of natural seismicity, but underlying mechanisms remain debated. Here, we experimentally explore the presence or absence of aftershocks during failure of intact rock and slip on newly created laboratory faults. We show that the overall activity increase and spatial localization of acoustic emission (...

Plain Language Summary While it is known that fluid injection operations can induce seismic activity, it has remained unclear how this activity compares to their natural counterpart, seismic swarms driven by natural fluid flows. The latter are typically characterized by the absence of a dominant event within the seismic sequence, while exhibiting o...

The behavior of granular media under quasistatic loading has recently been shown to attain a stable evolution state corresponding to a manifold in the space of micromechanical variables. This state is characterized by sudden transitions between metastable jammed states, involving the partial micromechanical rearrangement of the granular medium. Usi...

The frictional instability associated with earthquake initiation and earthquake dynamics is believed to be mainly controlled by the dynamics of fragmented rocks within the fault gauge. Principal features of the emerging seismicity (e.g. intermittent dynamics and broad time and/or energy scales) have been replicated by simple experimental setups, wh...

Spreading processes on networks are ubiquitous in both human-made and natural systems. Understanding their behavior is of broad interest: from the control of epidemics to understanding brain dynamics. While in some cases there exists a clear separation of timescales between the propagation of a single spreading cascade and the initiation of the nex...

The behavior of granular media under quasi-static loading has recently been shown to attain a stable evolution state corresponding to a manifold in the space of micromechanical variables. This state is characterized by sudden transitions between metastable jammed states, involving the partial micromechanical rearrangement of the granular medium. Us...

Within the classical eye-blink conditioning, Purkinje cells within the cerebellum are known to suppress their tonic firing rates for a well defined time period in response to the conditional stimulus after training. The temporal profile of the drop in tonic firing rate, i.e., the onset and the duration, depend upon the time interval between the ons...

Prenatal stress (PS) can impact fetal brain structure and function and contribute to higher vulnerability to neurodevelopmental and neuropsychiatric disorders. To understand how PS alters evoked and spontaneous neocortical activity and intrinsic brain functional connectivity, mesoscale voltage imaging was performed in adult C57BL/6NJ mice that had...

Earthquakes can be induced by natural and anthropogenic processes involving the injection or migration of fluids within rock formations. A variety of field observations has led to the formulation of three different and apparently contradicting paradigms in the estimation of the seismic hazard associated with fluid injections. We introduce a unified...

Prenatal stress (PS) can impact fetal brain structure and function and lead to higher vulnerability to neurodevelopmental and neuropsychiatric disorders. To understand how PS alters evoked and spontaneous cortical activity and intrinsic brain functional connectivity, mesoscale voltage imaging was performed in adult C57BL/6NJ mice who were exposed t...

Earthquakes can be induced by natural and anthropogenic processes involving the injection or migration of fluids within rock formations. A variety of field observations has led to the formulation of three different and apparently contradicting paradigms in the estimation of the seismic hazard associated with fluid injections. Based on a unified con...

Crucial to the development of earthquake forecasting schemes is the manifestation of spatiotemporal correlations between earthquakes as highlighted, for example, by the notion of aftershocks. Here, we present an analysis of the statistical relation between subsequent magnitudes of a recently proposed self-similar aftershock rates model of seismicit...

We study reaction-diffusion systems beyond the Markovian approximation to take into account the effect of memory on the formation of spatiotemporal patterns. Using a non-Markovian Brusselator model as a paradigmatic example, we show how to use reductive perturbation to investigate the formation and stability of patterns. Focusing in detail on the H...

Recent precision functional mapping of individual human brains has shown that individual brain organization is qualitatively different from group average estimates and that individuals exhibit distinct brain network topologies. How this variability affects the connectivity within individual resting-state networks remains an open question. This is p...

Many infectious processes, such as human diseases or computer viruses, spread across complex networks following directed links. While in some cases there exists a clear separation of timescales between the propagation of one outbreak and the initiation of the next, there are also processes for which this is not the case, such as zoonotic diseases....

We study reaction-diffusion systems beyond the Markovian approximation to take into account the effect of memory on the formation of spatio-temporal patterns. Using a non-Markovian Brusse-lator model as a paradigmatic example, we show how to use reductive perturbation to investigate the formation and stability of patterns. Focusing in detail on the...

Crucial to the development of earthquake forecasting schemes is the manifestation of spatiotemporal correlations between earthquakes as highlighted, for example, by the notion of aftershocks. Here, we present an analysis of the statistical relation between subsequent magnitudes for a recently proposed self-similar aftershock rates model of seismici...

We study reaction-diffusion systems beyond the Markovian approximation to take into account the effect of memory on the formation of spatio-temporal patterns. Using a non-Markovian Brusselator model as a paradigmatic example, we show how to use reductive perturbation to investigate the formation and stability of patterns. Focusing in detail on the...

Within the classical eye-blink conditioning, Purkinje cells within the cerebellum are known to suppress their tonic firing rates for a well defined time period in response to the conditional stimulus after training. The temporal profile of the drop in tonic firing rate, i.e., the onset and the duration, depend upon the time interval between the ons...

The formation and stability of social hierarchies is a question of general relevance. Here, we propose a simple model for establishing social hierarchy via pair-wise interactions between individuals and investigate its stability. In each interaction or fight, the probability of "winning" depends solely on the relative societal status of the partici...

Supporting information for section 3. (PDF)

Supporting information for section 4. (PDF)

Power grids sustain modern society by supplying electricity and thus their stability is a crucial factor for our civilization. The dynamic stability of a power grid is usually quantified by the probability of its nodes' recovery to phase synchronization of the alternating current it carries, in response to external perturbation. Intuitively, the st...

Power grids sustain modern society by supplying electricity and thus their stability is a crucial factor for our civilization. The dynamic stability of a power grid is usually quantified by the probability of its nodes' recovery to phase synchronization of the alternating current it carries, in response to external perturbation. Intuitively, the st...

Permeability enhancing treatments such as hydraulic fracturing (HF) induce microseismic events with typical magnitudes in the −3.0 to −0.5 range, although significantly larger induced earthquakes up to 4.7 in moment magnitude have been reported. Diffusion of pore pressure away from the hydraulic fracture system is thought to be a primary controllin...

The total energy of acoustic emission (AE) events in externally stressed materials diverges when approaching macroscopic failure. Numerical and conceptual models explain this accelerated seismic release (ASR) as the approach to a critical point that coincides with ultimate failure. Here, we report ASR during soft uniaxial compression of three silic...

Neuronal avalanches have become an ubiquitous tool to describe the activity of large neuronal assemblies. The emergence of scale-free statistics with well-defined exponents has led to the belief that the brain might operate near a critical point. Yet not much is known in terms of how the different exponents arise or how robust they are. Using calci...

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible for deformation. Avalanche models involving critical failure have determined common universality classes for stick-slip processes...

For a system to exhibit spiral patterns one would expect its parts to behave synchronously, as in a Mexican wave. Proving the contrary, chemical oscillators have now been observed in a state comprising a spiral surrounding an asynchronous core.

Maximum entropy estimation is of broad interest for inferring properties of systems across many disciplines. Using a recently introduced technique for estimating the maximum entropy of a set of random discrete variables when conditioning on bivariate mutual informations and univariate entropies, we show how this can be used to estimate the direct n...

One of the main challenges of modern physics is to provide a systematic understanding of systems far from equilibrium exhibiting emergent behavior. Prominent examples of such complex systems include, but are not limited to the cardiac electrical system, the brain, the power grid, social systems, material failure and earthquakes, and the climate sys...

Chimera patterns, characterized by coexisting regions of phase coherence and incoherence, have so far been studied in non-conservative systems with dissipation. Here, we show that the formation of chimera patterns can also be observed in conservative Hamiltonian systems with nonlocal hopping in which both energy and particle number are conserved. E...

We study triggering processes in triaxial compression experiments under a constant displacement rate on sandstone and granite samples using spatially located acoustic emission events and their focal mechanisms. We present strong evidence that event-event triggering plays an important role in the presence of large-scale or macrocopic imperfections,...

The acoustic emission activity associated with recent rock fracture experiments under different conditions has indicated that some features of event-event triggering are independent of the details of the experiment and the materials used and are often even indistinguishable from tectonic earthquakes. While the event-event triggering rates or afters...

For induced microseismicity associated with hydraulic fracturing, the frequency-magnitude distribution is typically characterized by a falloff with increasing magnitude that is significantly faster than for seismicity along active fault systems. This characteristic may arise from a break in scale invariance, possibly due to mechanical layering that...

In many important systems exhibiting crackling noise --- intermittent avalanche-like relaxation response with power-law and, thus, self-similar distributed event sizes --- the "laws" for the rate of activity after large events are not consistent with the overall self-similar behavior expected on theoretical grounds. This is in particular true for t...

Reconstructing the structural connectivity between interacting units from observed activity is a challenge across many different disciplines. The fundamental first step is to establish whether or to what extent the interactions between the units can be considered pairwise and, thus, can be modeled as an interaction network with simple links corresp...

Maximum entropy estimation is of broad interest for inferring properties of systems across many different disciplines. In this work, we significantly extend a technique we previously introduced for estimating the maximum entropy of a set of random discrete variables when conditioning on bivariate mutual informations and univariate entropies. Specif...

While the existence of stable knotted and linked vortex lines has been established in many experimental and theoretical systems including excitable media, their existence in oscillatory systems has remained elusive. Using the Kuramoto model of coupled phase oscillators as a paradigmatic example, we present strong numerical evidence that stable knot...

We investigate the validity of a proposed generalized Omori-Utsu law for the aftershock sequences for the Landers, Hector Mine, Northridge and Superstition Hills earthquakes, the four largest events in the southern California catalogue we analyse. This law unifies three of the most prominent empirical laws of statistical seismology-the Gutenberg-Ri...

Spatiotemporal chaos in oscillatory and excitable media is often characterized by the presence of phase singularities called defects. Understanding such defect-mediated turbulence and its dependence on the dimensionality of a given system is an important challenge in nonlinear dynamics. This is especially true in the context of ventricular fibrilla...

The shape of the spatial aftershock decay is sensitive to the triggering mechanism and thus particularly useful for discriminating between static and dynamic stress triggering. For California seismicity, it has been recently recognized that its form is more complicated than typically assumed consisting of three different regimes with transitions at...

Dynamical networks – networks inferred from multivariate time series – have been widely applied to climate data and beyond, resulting in new insights into the underlying dynamics. However, these inferred networks can suffer from biases that need to be accounted for to properly interpret the results. Here, we report on a previously unrecognized bias...

The decay of the aftershock density with distance plays an important role in the discussion of the dominant underlying cause of earthquake triggering. Here, we provide evidence that its form is more complicated than typically assumed and that in particular a transition in the power law decay occurs at length scales comparable to the thickness of th...

Background Inorganic polyphosphate (polyP) is a highly charged polyanion capable of interacting with a number of molecular targets. This signaling molecule is released into the extracellular matrix by central astrocytes and by peripheral platelets during inflammation. While the release of polyP is associated with both induction of blood coagulation...

Hydraulic fracturing, a powerful completion technique used to enhance oil or gas production from impermeable strata, may trigger unintended earthquake activity. The primary basis for assessment of triggered and natural seismic hazard is the classic Gutenberg-Richter (G-R) relation, which expresses scale-independent behaviour of earthquake magnitude...

Recent results have suggested that the statistics of bursts in the solar wind vary with solar cycle. Here, we show that this variation is basically absent if one considers extreme bursts. These are defined as threshold-exceeding events over the range of high thresholds for which their number decays as a power law. In particular, we find that the di...

[1] Based on an analysis of the direction of maximum horizontal compressive stress as a function of depth as observed at different scientific wells along the San Andreas fault, it has recently been suggested that the scale-invariant fluctuations in the stress orientation over intervals from tens of centimeters to several kilometers are directly rel...

We demonstrate for the first time that spiral wave chimeras-spiral waves with spatially extended unsynchronzied cores-can exist in complex oscillatory and even locally chaotic homogeneous systems under nonlocal coupling. Using ideas from phase synchronization, we show in particular that the unsynchronized cores exhibit a distribution of different f...

[1] Applying a simple general procedure for identifying aftershocks, we investigate their statistical properties for a high-resolution earthquake catalog covering Southern California. We compare our results with those obtained by using other methods in order to show which features truly characterize aftershock sequences and which depend on the defi...

Recent work has shown that the topologies of functional climate networks are sensitive to El Niño events. One important interpretation of the findings was that parts of the globe act in correlated relationships which become weaker, on average, during El Niño periods (this was shown using monthly averaged data where no time lag is required, and with...

Record-breaking avalanches generated by the dynamics of several driven nonlinear threshold models are studied. Such systems are characterized by intermittent behavior, where a slow buildup of energy is punctuated by an abrupt release of energy through avalanche events, which usually follow scale-invariant statistics. From the simulations of these s...

Maternal folic acid supplementation is essential to reduce the risk of neural tube defects. We hypothesize that high levels of folic acid throughout gestation may produce neural networks more susceptible to seizure in offspring. We hence administered large doses of folic acid to rats before and during gestation and found their offspring had a 42% d...

The Silences of the Archives, the Reknown of the Story. The Martin Guerre affair has been told many times since Jean de Coras and Guillaume Lesueur published their stories in 1561. It is in many ways a perfect intrigue with uncanny resemblance, persuasive deception and a surprizing end when the two Martin stood face to face, memory to memory, befor...

Spiral wave meander is a typical feature observed in cardiac tissue and in excitable media in general. Here, we show for a simple model of excitable cardiac tissue that a transition to alternans-a beat-to-beat temporal alternation in the duration of cardiac excitation-can also induce a transition in the spiral core motion that is related to the pre...

One of the hallmarks of our current understanding of seismicity as highlighted by the epidemic-type-aftershock sequence model is that the magnitudes of earthquakes are independent of one another and can be considered as randomly drawn from the Gutenberg-Richter distribution. This assumption forms the basis of many approaches for forecasting seismic...

Extreme events are an important theme in various areas of science because of their typically devastating effects on society and their scientific complexities. The latter is particularly true if the underlying dynamics does not lead to independent extreme events as often observed in natural systems. Here, we focus on this case and consider stationar...

Extreme events are of large interest in many fields of research because of their typically devastating effects on society and their scientific complexities. The latter is particularly true if the underlying dynamics does not lead to independent extreme events as often observed in natural systems. Here, we focus on this case and consider stationary...

Applying a recently introduced general statistical procedure for identifying aftershocks based on complex network theory, we investigate the statistical properties of aftershocks for a high-resolution earthquake catalog covering Southern California. In comparison with earlier studies of aftershock sequences, we show that many features depend sensit...

The statistical characterization and prediction of bursts in solar activity and in the solar wind is a problem of great practical relevance in space weather physics. Here, we show that many of the apparent qualitative and quantitative differences in burst statistics between solar activity and solar wind variation during solar maximum can be resolve...

We study the nontrivial clustering properties of extreme or recurrent events in the context of deterministic chaotic systems. We find that correlations between return times of such events can depend nonmonotonically on the threshold used to define the events, which leads to counterintuitive behavior. In particular, the distribution of the condition...

Experiments and theoretical studies show that filament turbulence in bounded three-dimensional media can arise due to a number of different mechanisms or instabilities. In this paper, we show that in oscillatory media, as described by the complex Ginzburg-Landau equation, these different instabilities generate different turbulent filament behaviors...