Seismic Hazard for Selected Sites in Greece: A Bayesian Estimate of Seismic Peak Ground Acceleration

A procedure for estimating maximum values of seismic peak ground accelerationat the examined site and quantiles of its probabilistic distribution in a future timeinterval of a given length is considered. The input information for the method areseismic catalog and regression relation between peak seismic acceleration at a givenpoint and magnitude and distance from the site to epicenter (seismic attenuation law).The method is based on Bayesian approach, which simply accounts for influenceof uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sitesin Greece.     

Maximum Earthquakes in Future Time Intervals

Izvestiya, Physics of the Solid Earth - Abstract—The paper addresses the problems associated with the maximum earthquakes in a seismically active region. Pisarenko and Rodkin (2009; 2010;...     

On the coherence between changes in biota and geomagnetic reversals in the Phanerozoic

The data on geomagnetic reversals, organic changes, and lower-mantle plume magmatism in the Phanerozoic are collected and correlated. No direct relationship is revealed between the geomagnetic reversals, plumes, and biozones. However, the frequency of geomagnetic reversals is found to correlate to the frequency of biozonal alterations. We relate this inconsistency to the coupling of the two processes, which are mutually independent, with the long-term changes in the Earth’s rotation. The plumes are formed at the core-mantle boundary and, thus, the reversals should have a different source. We hypothesize that the change in the geomagnetic polarity is due to the nonuniform rotation of the inner core relative to the mantle in combination with the changes in the axial tilt of the Earth’s rotation.     

On the synchronism in the events within the core and on the surface of the earth: the changes in the organic world and in the polarity of the geomagnetic field in the phanerozoic

The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes in the organic world.     

Seismic catastrophe in Japan on March 11, 2011: Long-term prediction on the basis of low-frequency microseisms

This paper presents a software technique for analyzing the multidimensional time series of microseismic oscillations on the basis of over 14 years of continuous observations, from early 1997 to February 2011, at F-net (Japan) broadband seismic stations. An analysis of the multifractal parameters of low-frequency microseismic noise allowed us to hypothesize, in as early as 2008, that Japanese Islands were approaching a large seismic catastrophe, the signature of which was a statistically significant decrease in the support width of the multifractal singularity spectrum. Subsequently, as new data became available and after some new statistics of microseismic noise (such as a logarithm of noise variance and an index of linear predictability) were included in joint analysis, we obtained some new results, indicating the facts that the parameters of the microseismic background had been increasingly synchronized (the synchronization process was estimated to start in mid-2002) and that the seismic danger had permanently grown. A cluster analysis of background parameters led us to conclude that in mid-2010 the islands of Japan entered a critically dangerous developmental phase of seismic process. The prediction of the catastrophe, first in terms of approximate magnitude (mid-2008) and then in terms of approximate time (mid-2010), was documented in advance in a series of papers and in proceedings at international conferences.     

Synchronization trends and rhythms of multifractal parameters of the field of low-frequency microseisms

The field of low-frequency microseisms is investigated with the use of data from 83 stations of the F-net broadband network in Japan over the period from the beginning of 1997 through June 2008. Vertical components with a sampling step of 1 s are used for analysis, as well as signals with a sampling step of 1 min obtained from the initial data by averaging and thinning. Long-period regularities of changes in the singularity spectrum support width Δα and the generalized Hurst exponent α* for the field of low-frequency microseisms were revealed by estimating multifractal singularity spectra in consecutive time windows 30 min long for 1-s data and 24 hour long for 1-min data. The average value of the parameter α* for 1-s data significantly decreased before the Hokkaido earthquake of September 25, 2003 (M = 8.3), and was not restored subsequently to its previous level. Prior to September 2003, 1-min data on α* variations experienced strong annual changes, which completely ceased afterwards. Both these effects are interpreted as an increase in the degree of synchronization of microseismic noise on Japan’s islands after the September 25, 2003, earthquake. This hypothesis is also supported by estimates of the measures of correlation and spectral coherence between variations in the average values of Δα and α* calculated for 1-min data inside five spatial clusters of stations from consecutive time fragments two months long. Based on the well-known statement of the theory of catastrophes that synchronization is one of the flags of an approaching catastrophe, it was suggested that the Hokkaido event could be a foreshock of an even stronger earthquake nucleating in the region of Japan’s islands.     

Cyclic Properties of Seismic Noise and the Problem of Predictability of the Strongest Earthquakes in Japanese Islands

Izvestiya, Atmospheric and Oceanic Physics - The results of an analysis of the properties of low-frequency seismic noise in the Japanese Islands from early 1997 to March 2018 are presented. The...     

Wavelet packet polarization method for an automatic detection of P and S wave arrivals

A new method is proposed for detecting P and S wave arrivals in the problem of passive seismic monitoring. This method is based on the wavelet packet decomposition of three-component seismic traces, their automatic quality control, and the calculation of the principal components of the traces in overlapping packet frequency bands and in scale-dependent moving time windows. The wave arrivals times are estimated by means of a robust iterative procedure of adjusting hyperbolic traveltime curves to the initial estimates of arrival times determined from the maximum values of the multilevel measure of the nonstationarity of each trace. The method has been developed for applications in the cases of a large number of bad single-component traces and a high noise level. To illustrate its application, the method is applied to the data set of the Cotton Valley experiment on the seismic monitoring of hydraulic fractures in a fractured gas reservoir.     

Wavelet-Aggregated Signal in Earthquake Prediction

The concept of aggregated signal is introduced. Quantitatively, an aggregated signal can be defined as the scalar signal: it accumulates in its own variations only those spectral components that are presented simultaneously in each scalar time series of the multidimensional signal to be analyzed. Moreover, an algorithm of aggregation is proposed to suppress the spectral components that are present in any of the scalar components but absent in others (these components can be called local disturbance signals, for instance of technogenic nature). The main purpose of constructing the aggregated signal is to make clearer the common tendency of low-frequency data-flow in geophysical networks, which indicates an increase in collective behavior.It is known that almost all models of the process of earthquake preparation have pointed out an increase in collective behavior of components of geophysical fields in the region of preparation when the coming geocatastrophe has entered its long- and mid-term stages. Long     

Lake Baikal: Extreme level as a rare hydrological event

The optimal boundaries of water level variation range in Lake Baikal have been determined under the conditions of runoff regulation at the Irkutsk HPP and the extremely low water abundance in lake basin in recent years. The properties of the time series of level regime and the characteristics of runoff from its drainage basin have been studied. The formation of long-term dry periods in the region has been studied, and the regularities in level regime variations in the lake have been estimated for both natural and runoff-regulation conditions, and the specifics of runoff regulation and level drawdown in dry years have been considered.