Medium-Term Earthquake Forecast Method Map of Expected Earthquakes: Results and Prospects

Izvestiya, Atmospheric and Oceanic Physics - This paper is the first in a series of studies generalizing the Map of Expected Earthquakes (MEE) medium-term earthquake forecast method and analyzing...     

The aftershock dynamics of the Sumatra-Andaman earthquake

The aftershocks of the catastrophic Sumatra-Andaman earthquake of December 26, 2004 (M = 9.0) are analyzed in the general context of the theory of critical phenomena. The analysis relies on the idea that, according to this theory, critical transitions have two key properties. The first is that the intensity of the fluctuations in a dynamical system monotonically increases with the approach of the bifurcation point, so that at a certain time instant, a sufficiently strong internal pulse initiates the catastrophe. This transition can be treated as spontaneous. The second property is that the reactance of the dynamical system drastically increases on the approach of the bifurcation. Even a weak external perturbation in the near-threshold interval can result in a catastrophe. In this case, it is reasonable to refer to the critical transition as an induced transition. The aftershocks of the Sumatra-Andaman earthquake are likely to demonstrate the typical features of induced seismicity. First, the strongest aftershock (M = 7.2) occurred 3 h 20 min after the main shock. It could have probably been induced by the round-trip seismic echo. Second, it was found that the spectral density of the aftershock sequence significantly increases at about ～0.3 mHz, which is close to the frequency of the spheroidal mode ₀S₂. This suggests that the spheroidal oscillations of the Earth, which are excited by the main seismic shock, modulate the aftershock activity. Both hypotheses are supported by the analysis of the aftershocks of the Tohoku earthquake of March 11, 2011 (M = 9.0).     

Content and Composition of Hydrocarbons in Water and Sediments in the Area of Kerch Strait

Doklady Earth Sciences - The results of studying the content and composition of aliphatic hydrocarbons (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in the suspended particulate matter of the...     

On the Time Dependences of the Fracture Concentration Parameter Estimated by Different Methods

Doklady Earth Sciences - The time dependences of the fracture concentration parameter characterizing the process of accumulation of defects formed in loaded objects, i.e., steel specimens in...     

Dependence of the aftershock flow on the main shock magnitude

Previously, we predicted and then observed in practice the property of aftershocks which consists in the statistically regular clustering of events in time during the first hours after the main shock. The characteristic quasi-period of clustering is three hours. This property is associated with the cumulative action of the surface waves converging to the epicenter, whereas the quasi-period is mainly determined by the time delay of the round-the-world seismic echo. The quasi-period varies from case to case. In the attempt to find the cause of this variability, we have statistically explored the probable dependence of quasi-period on the magnitude of the main shock. In this paper, we present the corresponding result of analyzing global seismicity from the USGS/NEIC earthquake catalog. We succeeded in finding a significant reduction in the quasiperiod of the strong earthquakes clustering with growth in the magnitude of the main shock. We suggest the interpretation of this regularity from the standpoint of the phenomenological theory of explosive instability. It is noted that the phenomenon of explosive instability is fairly common in the geophysical media. The examples of explosive instability in the radiation belt and magnetospheric tail are presented. The search for the parallels in the evolution of explosive instability in the lithosphere and magnetosphere of the Earth will enrich both the physics of the earthquakes and physics of the magnetospheric pulsations.     

Macroseismic manifestations of the Okhotsk earthquake of May 24, 2013 in the territory of Moscow

The results of a study of the macroseismic effects in the territory of Moscow of a remote deepfocus earthquake that occurred on May 24, 2013 in the Sea of Okhotsk are reported. On the surface of the earth and on the first floors of the buildings the seismic effect was not felt. The effect of the shock began to manifest itself at levels higher than the fifth floor of the buildings. The distribution of points on the map where the earthquake was felt is non-uniform. Points where tremor was felt do not appear to correspond with certain types of Quaternary deposits or with zones of different depth. There is also no significant correlation of the parts of the surface with high intensities of tremor and areas of ground-water flooding. Comparison between the surface manifestations of the seismic event and the tectonic features and deep structure of the metropolis was made. Based on the results of the implemented statistical estimation of distribution points where the earthquake was felt on the territory of the city it is visible that fault zones govern the largest number of points, while block structures characterize almost half of them. Thus, we can reasonably suggest a certain macroseismic increase of vibrations from earthquakes in the areas of large faults in the city. The study of deformations of the asphalt cover of walkways on the landslide-affected slope of Vorobyovy Hills showed that the tremor caused by the Okhotsk deep focus earthquake of May 24, 2013, caused the activation of a small landslide at all levels of the hillside.     

Case 25 application of the concentration parameter of seismoactive faults to Southern California

In this paper we evaluate the present state of the seismic regime in Southern California using the concentration parameter of seismogenic faults (K _sf ,Sobolev andZavyalov, 1981). The purpose of this work is to identify potential sites for large earthquakes during the next five or ten years. The data for this study derived from the California Institute of Technology's catalog of southern California earthquakes, and spanned the period between 1932 to June 1982. We examined events as small asM _L 1.8 but used a magnitude cutoff atM _L =3.3 for a detailed analysis. The size of the target earthquakes (M _M ) was chosen as 5.3 and 5.8.The algorithm for calculatingK _sf used here was improved over the algorithm described bySobolev andZavyalov (1981) in that it considered the seismic history of each elementary seismoactive volume. The dimensions of the elementary seismoactive volumes were 50 km×50 km and 20 km deep. We found that the mean value ofK _sf within 6 months prior to the target events was 6.1±2.0 for target events withM _L 5.3 and 5.41.8 for targets withM _L 5.8. Seventy-three percent of the targets withM _L 5.8 occurred in areas whereK _sf was less than 6.1. The variance of the time between the appearance of areas with lowK _sf values and the following main shocks was quite large (from a few months to ten years) so this parameter cannot be used here for accurate predictions of occurrence time.Regions where the value ofK _sf was below 6.1 at the end of our data set (June, 1982) are proposed as the sites of target earthquakes during the next five to ten years. The most dangerous area is the area east of San Bernardino whereK _sf values are presently between 2.9 and 3.7 and where there has been no earthquake withM _L 5.3 since 1948.