Model for triggering of non-volcanic tremor by earthquakes

There is evidence of tremor triggering by seismic waves emanating from distant large earthquakes. The frequency content of both triggered and ambient tremor are largely identical, suggesting that this property does not depend directly on the nature of the source. We show here that the model of plate dynamics developed earlier by us is an appropriate tool for describing tremor triggering. In the framework of this model, tremor is an internal response of a fault to a failure triggered by external disturbances. The model predicts generation of radiation in a frequency range defined by the fault parameters. Thus, although the amplitude and duration of a tremor burst may reflect the "personality" of the source, the frequency content does not. The model also explains why a tremor has no clear impulsive phase, in contrast to earthquakes. The relationship between tremor and low frequency earthquakes is discussed.Comment: 9 pages, 1 figur

Relaxation rates of the linearized Uehling-Uhlenbeck equation for bosons

We linearize the Uehling-Uhlenbeck equation for bosonic gases close to thermal equilibrium under the assumption of a contact interaction characterized by a scattering length a. We show that the spectrum of relaxation rates is similar to that of a classical hard-sphere gas. However, the relaxation rates show a significant dependence on the fugacity z of the gas, increasing by as much as 60% of their classical value for z approaching 1. The relaxation modes are also significantly altered at higher values of z. The relaxation rates and modes are determined by the eigenvalues and eigenvectors of a Fredholm integral operator of the second kind. We derive an analytical form for the kernel of this operator and present numerical results for the first few eigenvalues and eigenvectors.Robert A. Welch Foundation F-1051Physic

Model of deep non-volcanic tremor part I: ambient and triggered tremor

There is evidence of triggering of tremor by seismic waves emanating from distant large earthquakes. The frequency contents of triggered and ambient tremor are largely identical, suggesting that tremor does not depend directly on the nature of the source. We show here that the model of plate dynamics developed earlier by us is an appropriate tool for describing the onset of tremor. In the framework of this model, tremor is an internal response of a fault to a failure triggered by external disturbances. The model predicts generation of radiation in a frequency range defined by the fault parameters. Other specific features predicted are: the upper limit of the size of the emitting area is a few dozen km; tremor accompanies earthquakes and aseismic slip; the frequency content of tremor depends on the type of failure. The model also explains why a tremor has no clear impulsive phase, in contrast to earthquakes. A comparatively small effective normal stress (hence a high fluid pressure) is required to make the model consistent with observed tremor parameters. Our model indicates that tremor is not necessarily a superposition of low frequency earthquakes, as commonly assumed, although the latter may trigger them. The approach developed complements the conventional viewpoint which assumes that tremor reflects a frictional process with low rupture speed. Essentially our model adds the hypothesis that resonant-type oscillations exist inside a fault. This addition may change our understanding of the nature of tremor in general, and the methods of its identification and location in particular.Comment: 32 pages, 16 figures. arXiv admin note: text overlap with arXiv:1202.091

Productivity developments abroad

This article reviews recent productivity trends in foreign industrial countries. The focus of the analysis is on whether productivity abroad has accelerated to an extent comparable to that observed in the United States. The authors find that foreign labor productivity, unlike that of the United States, has not accelerated in the latter half of the 1990s and discuss the role played by information technology in influencing foreign productivity trends as well as cyclical and methodological factors that are important in the analysis of these trends.Productivity ; Information technology ; Labor productivity

The expectations trap hypothesis

This article explores a hypothesis about the take-off in inflation in the early 1970s. According to the expectations trap hypothesis, the Fed was driven to high money growth by a fear of violating the expectations of high inflation that existed at the time. The authors argue that this hypothesis is more compelling than the Phillips curve hypothesis, according to which the Fed produced the high inflation as an unfortunate by product of a conscious decision to jump start a weak economy.Inflation (Finance) ; Phillips curve

The expectations trap hypothesis

The authors examine the inflation take-off of the early 1970s in terms of the expectations trap hypothesis, according to which fear of violating the public’s inflation expectations pushed the Fed into producing high inflation. This interpretation is compared with the Phillips curve hypothesis, according to which the Fed produced high inflation as the unfortunate byproduct of a conscious decision to jump-start a weak economy. Which hypothesis is more plausible has important implications for what should be done to prevent future inflation flare-ups.Inflation (Finance) ; Phillips curve ; Economic conditions - United States

How does dissipation affect the transition from static to dynamic macroscopic friction?

Description of the transitional process from a static to a dynamic frictional regime is a fundamental problem of modern physics. Previously we developed a model based on the well-known Frenkel-Kontorova model to describe dry macroscopic friction. Here this model has been modified to include the effect of dissipation in derived relations between the kinematic and dynamic parameters of a transition process. The main (somewhat counterintuitive) result is a demonstration that the rupture (i.e. detachment front) velocity of the slip pulse which arises during the transition does not depend on friction. The only parameter (besides the elastic and plastic properties of the medium) controlling the rupture velocity is the shear to normal stress ratio. In contrast to the rupture velocity, the slip velocity does depend on friction. The model we have developed describes these processes over a wide range of rupture and slip velocities (up to 7 orders of magnitude) allowing, in particular, the consideration of seismic events ranging from regular earthquakes, with rupture velocities on the order of a few km/s, to slow slip events, with rupture velocities of a few km/day.Comment: 21 pages, 12 figure

Trade Integration, Competiton, and the Decline in Exchange-rate Pass-through

Over the past twenty years, U.S. import prices have become less responsive to the exchange rate. We propose that this decline is a result of increased trade integration. To illustrate this effect, we develop an open economy DGE model in which there is strategic complementarity in price setting so that a firm's pricing decision depends on the prices set by its competitors. Because of the complementarity in price setting, a foreign exporter finds it optimal to vary its markup over cost in response to shocks that change the exchange rate, which insulates import prices from exchange rate movements. With increased trade integration, exporters have become more responsive to the prices of their competitors and this change in pricing behavior accounts for a significant portion of the observed decline in the sensitivity of U.S import prices to the exchange rate. Our environment of low pass-through also has important implications for the welfare benefits of trade integration: we find that the benefits are substantially reduced compared to an environment with complete pass-through.Pass-through, Trade Integration, Strategic Complementarities