title: Anomalous fluctuations of vertical velocity of Earth and their possible implications for earthquakes.
abstract: High-quality measurements of seismic activities around the world provide a wealth of data and information that are relevant to understanding of when earthquakes may occur. If viewed as complex stochastic time series, such data may be analyzed by methods that provide deeper insights into their nature, hence leading to better understanding of the data and their possible implications for earthquakes. In this paper, we provide further evidence for our recent proposal [P. Mansour, Phys. Rev. Lett. 102, 014101 (2009)10.1103/PhysRevLett.102.014101] for the existence of a transition in the shape of the probability density function (PDF) of the successive detrended increments of the stochastic fluctuations of Earth's vertical velocity V_{z} , collected by broadband stations before moderate and large earthquakes. To demonstrate the transition, we carried out extensive analysis of the data for V_{z} for 12 earthquakes in several regions around the world, including the recent catasrophic one in Haiti. The analysis supports the hypothesis that before and near the time of an earthquake, the shape of the PDF undergoes significant and discernable changes, which can be characterized quantitatively. The typical time over which the PDF undergoes the transition is about 5-10 h prior to a moderate or large earthquake.
authors.affiliation: Department of Physics, Sharif University of Technology, Tehran 11155-9161, Iran.
authors.forename: Pouya
authors.initials: P
authors.lastname: Manshour
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Ghasemi
authors.forename: T
authors.initials: T
authors.lastname: Matsumoto
authors.forename: J
authors.initials: J
authors.lastname: Gómez
authors.forename: Muhammad
authors.initials: M
authors.lastname: Sahimi
authors.forename: J
authors.initials: J
authors.lastname: Peinke
authors.forename: A F
authors.initials: AF
authors.lastname: Pacheco
authors.forename: M Reza Rahimi
authors.initials: MR
authors.lastname: Tabar