A simple definition of the duration of strong earthquake ground motion based on the mean-square integral of motion has been presented. It is closely related to that part of the strong motion which contributes significantly to the seismic energy as recorded at a point and to the related spectral amplitudes. Correlations have been established between the duration of strong-motion acceleration, ve...

Dear Editor-in-Chief On January 28, the city of Khoy (the northwest of Iran) was struck by a strong earthquake with a magnitude of 5.9 on the Richter scale at 21:44:44 and a depth of 7 km, X: 45.01 and Y: 38.05 (1). This earthquake occurred 117 kilometers from Urmia, the capital of the West Azerbaijan Province. Over 370,000 people were affected by this earthquake, which resulted in three death...

Introduction In recent years, large earthquakes have occurred frequently all over the world.1-5 Earthquakes cause a large number of casualties with their catastrophic force. On May 12, 2008, an earthquake of 8.0 magnitude occurred in Wenchuan, Sichuan Province, in China. By May 25, 2008, 68,712 people had died, 374,640 were wounded, and 17,042 were reported missing. On January 12, 2010, a 7.3-m...

Low-frequency spectra for the 1989 Macquarie Ridge earthquake (magnitude 8.2) show an amplitude increase and a phase-delay decrease below 6 millihertz that require a short-term slow precursor. This earthquake can be modeled as a compound event in which a fast-rupturing, ordinary earthquake was initiated by an episode of slow, smooth deformation that began more than 100 seconds before the main s...

A semi-Markov model estimating the waiting times and magnitudes of large earthquakes is proposed. The model defines a discrete-time, discrete-state process in which successive state occupancies are governed by the transition probabilities of the Markov process. The stay in any state is described by an integer-valued random variable that depends on the presently occupied state and the state to w...

during the past decades, attempts have been made to develop an early warning system for coming destructive earthquakes a few seconds before the ongoing ground motion. in this paper, a practical method for the early warning of earthquakes in south iran is presented. this region is selected for study because it has high potential for generating earthquakes and has a more complete strong ground mo...

Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran eart...

[1] We examine five different methods to estimate an earthquake’s magnitude using only P wave data for use in earthquake early warning systems. We test two input parameters: the maximum predominant period of the P wave (τp) and the displacement amplitude of the P wave’s vertical component (Pd). We apply our algorithms to 174 earthquakes 3.0<M< 8.0 from California and Japan that have also been u...