Analysis of earthquake body wave spectra for potency and magnitude values: implications for magnitude scaling relations

We develop a simple methodology for reliable automated estimation of the low-frequency asymptote in seismic body wave spectra of small to moderate local earthquakes. The procedure corrects individual P- and S-wave spectra for propagation and site effects and estimates the seismic potency from a stacked spectrum. The method is applied to >11 000 earthquakes with local magnitudes 0 < M_L < 4 that occurred in the Southern California plate-boundary region around the San Jacinto fault zone during 2013. Moment magnitude M_w values, derived from the spectra and the scaling relation of Hanks & Kanamori, follow a Gutenberg–Richter distribution with a larger b-value (1.22) from that associated with the M_L values (0.93) for the same earthquakes. The completeness magnitude for the M_w values is 1.6 while for M_L it is 1.0. The quantity (M_w – M_L) linearly increases in the analysed magnitude range as M_L decreases. An average earthquake with M_L = 0 in the study area has an M_w of about 0.9. The developed methodology and results have important implications for earthquake source studies and statistical seismology

On-demand or Spot? Selling the cloud to risk-averse customers

In Amazon EC2, cloud resources are sold through a combination of an on-demand market, in which customers buy resources at a fixed price, and a spot market, in which customers bid for an uncertain supply of excess resources. Standard market environments suggest that an optimal design uses just one type of market. We show the prevalence of a dual market system can be explained by heterogeneous risk attitudes of customers. In our stylized model, we consider unit demand risk-averse bidders. We show the model admits a unique equilibrium, with higher revenue and higher welfare than using only spot markets. Furthermore, as risk aversion increases, the usage of the on-demand market increases. We conclude that risk attitudes are an important factor in cloud resource allocation and should be incorporated into models of cloud markets.Comment: Appeared at WINE 201

Control theory for principled heap sizing

We propose a new, principled approach to adaptive heap sizing based on control theory. We review current state-of-the-art heap sizing mechanisms, as deployed in Jikes RVM and HotSpot. We then formulate heap sizing as a control problem, apply and tune a standard controller algorithm, and evaluate its performance on a set of well-known benchmarks. We find our controller adapts the heap size more responsively than existing mechanisms. This responsiveness allows tighter virtual machine memory footprints while preserving target application throughput, which is ideal for both embedded and utility computing domains. In short, we argue that formal, systematic approaches to memory management should be replacing ad-hoc heuristics as the discipline matures. Control-theoretic heap sizing is one such systematic approach

Statistics of Earthquakes in Simple Models of Heterogeneous Faults

Simple models for ruptures along a heterogeneous earthquake fault zone are studied, focussing on the interplay between the roles of disorder and dynamical effects. A class of models are found to operate naturally at a critical point whose properties yield power law scaling of earthquake statistics. Various dynamical effects can change the behavior to a distribution of small events combined with characteristic system size events. The studies employ various analytic methods as well as simulations.Comment: 4 pages, RevTex, 3 figures (eps-files), uses eps

Universal mean moment rate profiles of earthquake ruptures

Earthquake phenomenology exhibits a number of power law distributions including the Gutenberg-Richter frequency-size statistics and the Omori law for aftershock decay rates. In search for a basic model that renders correct predictions on long spatio-temporal scales, we discuss results associated with a heterogeneous fault with long range stress-transfer interactions. To better understand earthquake dynamics we focus on faults with Gutenberg-Richter like earthquake statistics and develop two universal scaling functions as a stronger test of the theory against observations than mere scaling exponents that have large error bars. Universal shape profiles contain crucial information on the underlying dynamics in a variety of systems. As in magnetic systems, we find that our analysis for earthquakes provides a good overall agreement between theory and observations, but with a potential discrepancy in one particular universal scaling function for moment-rates. The results reveal interesting connections between the physics of vastly different systems with avalanche noise.Comment: 13 pages, 5 figure

Gutenberg Richter and Characteristic Earthquake Behavior in Simple Mean-Field Models of Heterogeneous Faults

The statistics of earthquakes in a heterogeneous fault zone is studied analytically and numerically in the mean field version of a model for a segmented fault system in a three-dimensional elastic solid. The studies focus on the interplay between the roles of disorder, dynamical effects, and driving mechanisms. A two-parameter phase diagram is found, spanned by the amplitude of dynamical weakening (or ``overshoot'') effects (epsilon) and the normal distance (L) of the driving forces from the fault. In general, small epsilon and small L are found to produce Gutenberg-Richter type power law statistics with an exponential cutoff, while large epsilon and large L lead to a distribution of small events combined with characteristic system-size events. In a certain parameter regime the behavior is bistable, with transitions back and forth from one phase to the other on time scales determined by the fault size and other model parameters. The implications for realistic earthquake statistics are discussed.Comment: 21 pages, RevTex, 6 figures (ps, eps

Analysis of earthquake body wave spectra for potency and magnitude values: implications for magnitude scaling relations

We develop a simple methodology for reliable automated estimation of the low-frequency asymptote in seismic body wave spectra of small to moderate local earthquakes. The procedure corrects individual P- and S-wave spectra for propagation and site effects and estimates the seismic potency from a stacked spectrum. The method is applied to >11 000 earthquakes with local magnitudes 0 < M_L < 4 that occurred in the Southern California plate-boundary region around the San Jacinto fault zone during 2013. Moment magnitude M_w values, derived from the spectra and the scaling relation of Hanks & Kanamori, follow a Gutenberg–Richter distribution with a larger b-value (1.22) from that associated with the M_L values (0.93) for the same earthquakes. The completeness magnitude for the M_w values is 1.6 while for M_L it is 1.0. The quantity (M_w – M_L) linearly increases in the analysed magnitude range as M_L decreases. An average earthquake with M_L = 0 in the study area has an M_w of about 0.9. The developed methodology and results have important implications for earthquake source studies and statistical seismology

Molecular Dynamics Simulations of Weak Detonations

Detonation of a three-dimensional reactive non-isotropic molecular crystal is modeled using molecular dynamics simulations. The detonation process is initiated by an impulse, followed by the creation of a stable fast reactive shock wave. The terminal shock velocity is independent of the initiation conditions. Further analysis shows supersonic propagation decoupled from the dynamics of the decomposed material left behind the shock front. The dependence of the shock velocity on crystal nonlinear compressibility resembles solitary behavior. These properties categorize the phenomena as a weak detonation. The dependence of the detonation wave on microscopic potential parameters was investigated. An increase in detonation velocity with the reaction exothermicity reaching a saturation value is observed. In all other respects the model crystal exhibits typical properties of a molecular crystal.Comment: 38 pages, 20 figures. Submitted to Physical Review

Utility of the ACC/AHA Lesion Classification to Predict Outcomes After Contemporary DES Treatment:Individual Patient Data Pooled Analysis From 7 Randomized Trials

BACKGROUND: Use of the modified American College of Cardiology (ACC)/American Heart Association (AHA) lesion classification as a prognostic tool to predict short‐ and long‐term clinical outcomes after percutaneous coronary intervention in the modern drug‐eluting stent era is uncertain. METHODS AND RESULTS: Patient‐level data from 7 prospective, randomized trials were pooled. Clinical outcomes of patients undergoing single lesion percutaneous coronary intervention with second‐generation drug‐eluting stent were analyzed according to modified ACC/AHA lesion class. The primary end point was target lesion failure (TLF: composite of cardiac death, target vessel myocardial infarction, or ischemia‐driven target lesion revascularization). Clinical outcomes to 5 years were compared between patients treated for noncomplex (class A/B1) versus complex (class B2/C) lesions. Eight thousand five hundred sixteen patients (age 63.1±10.8 years, 70.5% male) were analyzed. Lesions were classified as A, B1, B2, and C in 7.9%, 28.5%, 33.7%, and 30.0% of cases, respectively. Target lesion failure was higher in patients undergoing percutaneous coronary intervention of complex versus noncomplex lesions at 30 days (2.0% versus 1.1%, P=0.004), at 1 year (4.6% versus 3.0%, P=0.0005), and at 5 years (12.4% versus 9.2%, P=0.0001). By multivariable analysis, treatment of ACC/AHA class B2/C lesions was significantly associated with higher rate of 5‐year target lesion failure (adjusted hazard ratio, 1.39 [95% CI, 1.17–1.64], P=0.0001) driven by significantly higher rates of target vessel myocardial infarction and ischemia‐driven target lesion revascularization. CONCLUSIONS: In this pooled large‐scale analysis, treating complex compared with noncomplex lesions according to the modified ACC/AHA classification with second‐generation drug‐eluting stent was associated with worse 5‐year clinical outcomes. This historical classification system may be useful in the contemporary era for predicting early and late outcomes following percutaneous coronary intervention

Anticoagulation in Patients With COVID-19: JACC Review Topic of the Week.

Clinical, laboratory, and autopsy findings support an association between coronavirus disease-2019 (COVID-19) and thromboembolic disease. Acute COVID-19 infection is characterized by mononuclear cell reactivity and pan-endothelialitis, contributing to a high incidence of thrombosis in large and small blood vessels, both arterial and venous. Observational studies and randomized trials have investigated whether full-dose anticoagulation may improve outcomes compared with prophylactic dose heparin. Although no benefit for therapeutic heparin has been found in patients who are critically ill hospitalized with COVID-19, some studies support a possible role for therapeutic anticoagulation in patients not yet requiring intensive care unit support. We summarize the pathology, rationale, and current evidence for use of anticoagulation in patients with COVID-19 and describe the main design elements of the ongoing FREEDOM COVID-19 Anticoagulation trial, in which 3,600 hospitalized patients with COVID-19 not requiring intensive care unit level of care are being randomized to prophylactic-dose enoxaparin vs therapeutic-dose enoxaparin vs therapeutic-dose apixaban. (FREEDOM COVID-19 Anticoagulation Strategy [FREEDOM COVID]; NCT04512079).Dr Farkouh has received research grants from Amgen, Novo Nordisk, and Novartis. Dr Stone has received speaker honoraria from Infraredx; has served as a consultant to Valfix, TherOx, Robocath, HeartFlow, Ablative Solutions, Miracor, Neovasc, Abiomed, Ancora, Vectorious, Elucid Bio, Occlutech, CorFlow, Apollo Therapeutics, Impulse Dynamics, Cardiomech, Gore, and Amgen; and has equity/ options from Ancora, Cagent, Applied Therapeutics, Biostar family of funds, SpectraWave, Orchestra Biomed, Aria, Cardiac Success, Valfix, and Xenter. Dr Godoy is supported by the Frederick Banting and Charles Best Canada Graduate Scholarship (Doctoral Research Award) from the Canadian Institutes of Health Research. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.S