Kamchatka Earthquakes Research Articles

Changes of geoacoustic emission directivity at «Mikizha» site associated with earthquakes in Kamchatka

To investigate high frequency geoacoustic emission, a receiving system based on a compound vector receiver was installed in Kamchatka. It allows the authors to determine the direction of sound wave arrival. In the result of data analysis for the period from August 2008 to January 2016, it was determined that anomalies of geoacoustic emission directivity occur during the majority of the earthquakes with Ks > 9.0 in the South of Kamchatka.

Calculation of seismic regime parameters on the basis of a probabilistic model of Kamchatka earthquake catalogue

In the present paper on the basis of a probabilistic interpretation of the earthquake repetition law, simple formulas were obtained which allow us from the known number of earthquake events in a representative interval of energy class (magnitude) to estimate the number of seismic events falling within an unrepresentative interval and the expected time of an earthquake with a magnitude exceeding the maximum registered values for the period of instrumental observations.

Ionospheric parameter modelling and anomaly discovery by combining the wavelet transform with autoregressive models

The paper is devoted to new mathematical tools for ionospheric parameter analysis and anomaly discovery during ionospheric perturbations. The complex structure of processes under study, their <em>a-priori</em> uncertainty and therefore the complex structure of registered data require a set of techniques and technologies to perform mathematical modelling, data analysis, and to make final interpretations. We suggest a technique of ionospheric parameter modelling and analysis based on combining the wavelet transform with autoregressive integrated moving average models (ARIMA models). This technique makes it possible to study ionospheric parameter changes in the time domain, make predictions about variations, and discover anomalies caused by high solar activity and lithospheric processes prior to and during strong earthquakes. The technique was tested on critical frequency foF2 and total electron content (TEC) datasets from Kamchatka (a region in the Russian Far East) and Magadan (a town in the Russian Far East). The mathematical models introduced in the paper facilitated ionospheric dynamic mode analysis and proved to be efficient for making predictions with time advance equal to 5 hours. Ionospheric anomalies were found using model error estimates, those anomalies arising during increased solar activity and strong earthquakes in Kamchatka.

Relationship between anomalous changes in magnetotelluric impedance and strong earthquakes in Kamchatka

Relationship between anomalous changes in magnetotelluric impedance and strong earthquakes in Kamchatka

Scaling properties of corner frequencies of Kamchatka earthquakes

Scaling properties of earthquake populations bear the major information on the physics of the source process of an earthquake. To determine scaling properties, source spectra of more than 400 earthquakes of Kamchatka were determined in a frequency range 0.1–30 Hz using materials of digital registration of PET station, and characteristic frequencies of earthquakes were estimated. The range of magnitudes is 4–6.5, the range of distances is 80–220 km. To enable reduction of a spectrum to the source, attenuation properties of the medium around PET were determined beforehand. It is revealed that source spectra show several corner (characteristic) frequencies: fc1, fc2 and fc3; where the spectral trend changes: from f0 to f−1, from f−1 to f−2, and from f−2 to f−3, respectively. Although in some cases fc1 ≈ fc2 in agreement with the usual ω−2 spectral model, the main part of spectra has more complicated character. For a large part of the studied earthquakes a source-controlled upper cutoff of acceleration spectrum, or corner frequency fc3, is observed. This is an important fact, as the existence of fc3 (source-controlled fmax) is not recognized in the bulk of the seismological literature. For fc1, the observed scaling agrees with the usual hypothesis of similarity of the earthquake sources of different size (magnitude); it is close to fc1 ∼ M0−1/3, where M0 is seismic moment. For fc2, scaling is close to fc2 ∼ M0−0.17 ∼ fc10.5, that indicates an expressed violation of similarity. For fc3, scaling is close to fc2 ∼ M0−0.08 ∼ fc10.25, so that similarity is broken even sharper in this case. Hypotheses about possible causes of the observed scaling are discussed.

Kamchatka subduction zone, May 2013: the Mw 8.3 deep earthquake, preceding shallow swarm and numerous deep aftershocks

A sequence of 98 teleseismically recorded earthquakes occurred off the east coast of Kamchatka at depths between 10-90 km around latitude 52.5°N and longitude 160°E on May 16–23, 2013. The swarm occurred along the northern limit of the rupture area of the 1952 Mw 9.0 great Kamchatka earthquake, the fifth largest earthquake in the history of seismic observations. On May 24, 2013 the strongest deep earthquake ever recorded of Mw 8.3 occurred beneath the Sea of Okhotsk at a depth of 610 km in the Pacific slab of the Kamchatka subduction zone, becoming the northernmost deep earthquake in the region. The deep Mw 8.3 earthquake occurred down-dip of the shallow swarm in a transition zone between the southern deep and northern shallow segments of the Pacific slab. Several deep aftershocks followed, covering a large, laterally elongated part of the slab. We suppose that the two described earthquake sequences, the May 16–23 shallow earthquake swarm and the May 24–28 deep mainshock-aftershock series, represent a single tectonic event in the Pacific slab having distinct properties at different depth levels. A low-angle underthrusting of the shallow part of the slab recorded by the shallow earthquake swarm activated the deep part; this process induced the deep mainshock-aftershock series only three days after the swarm. The domain of the subducting slab activated by the May 2013 earthquake occurrence was extraordinarily large both down-dip and along-strike.

On the question of influence of remote earthquakes on seismicity

The responses of the Kamchatka earthquakes with a minimum energy class of completeness K ≥ 8.5 to 214 strong worldwide earthquakes with magnitudes M ≥ 7.5 and to 40 earthquakes with M ≥ 8 are studied. The analysis covers the time interval of 1963–2012. The distances from the sources of the strongest earthquakes to the center of the seismically active Kamchatka zone range from 600 to 16000 km. It is established that the remote earthquakes enhanced seismic activity in Kamchatka, at least in the cases when the dynamic strain was above 10−6, which corresponds to the additional stresses of 10−2 MPa, accelerations above 0.1 cm/s2, and the periods of the surface waves of ∼20 s. The response to the remote events gradually increased within a few days. The sensitivity of the response to the remote earthquakes varied in the course of time, which is identified on the intervals of a few dozens of years.

Andaman-Sumatra island arc: II. The December 26, 2004 earthquake as one of the key episodes in seismogenic activation of the arc in the beginning of XXI century

The interpretation of the nature and parameters of the source for the earthquake that occurred in Sumatra on December 26, 2004 is suggested. Our study relies on a variety of data on the geological structure of the region, long-term seismicity, spatial distribution of the foreshocks and aftershocks, and focal mechanisms; and the pattern of shaking and tsunami, regularities in the occurrence of the earthquakes, and the genetic relationship between the seismic and geological parameters inherent in various types of seismogenic zones including island arcs. The source of the Sumatran earthquake is a steep reverse fault striking parallel to the island arc and dipping towards the ocean. The length of the fault is ∼450 km, and its probable bedding depth is ∼70–100 km. The magnitude of this seismic event corresponding to the length of its source is 8.9–9.0. The vertical displacement in the source probably reached 9–13 m. The fault is located near the inner boundary of the Aceh Depression between the epicenter of the earthquake and the northern tip of the depression. The strike-slip and strike-slip reverse the faults cutting the island arc form the northern and southern borders of the source. The location and source parameters in the suggested interpretation account quite well for the observed pattern of shaking and tsunami. The Aceh Depression and its environs probably also host other seismic sources in the form of large reverse faults. The Sumatran earthquake, which was the culmination of the seismogenic activation of the Andaman-Sumatra island arc in the beginning of XXI century, is a typical tsunamigenic island-arc earthquake. By its characteristics, this event is an analogue to the M W = 9 Kamchatka earthquake of November 4, 1952. The spatial distribution of the epicenters and the focal mechanisms of the aftershocks indicate that the repeated shocks during the Sumatran event were caused by the activation of a complex system of geological structures in various parts of the island arc and Andaman Sea instead of the slips on a single rupture (a subduction thrust about 1200–1300 km in length).

A parametric representation of Kamchatka seismicity over time

This paper presents a set of seismicity parameters that are estimated at the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences based on the regional catalog data with the purpose of routine monitoring of the current seismic situation in the region. The focus is on the identification of changes in the seismic regime (seismic quiescences and seismicity increases) in earth volumes adjacent to the maturing rupture zone of a large earthquake. The techniques we use include estimation of the seismicity level for the region using the SOUS’09 scale; calculation of the variations in the slope of the recurrence relation, identification of statistically significant anomalies in the slope using the Z test, and calculation of the seismic activity A10; monitoring the RTL parameter and variations in the area of seismogenic ruptures; using the Z test to detect areas of statistically significant decreases in the rate of seismicity; and identification of earthquake clusters. We furnish examples of such anomalies in these seismicity parameters prior to large earthquakes in Kamchatka.

Identifying the precursors of large (M ≥ 6.0) earthquakes in Kamchatka based on data from the Kamchatka Branch of the Russian expert council on earthquake prediction: 1998–2011

This paper describes the activities of the Kamchatka Branch of the Russian Expert Council on Earthquake Prediction, Assessment of Seismic Hazard and Risk (KB REC) over a 14 year period. We provide brief information on how the KB REC functions, the methods that are used for earthquake prediction in expert assessments, forecasts, and precursors of M ≥ 6.0 Kamchatka earthquakes for the 1998–2011 period. The efficiency of prediction using several methods is estimated.

Hardware complex for recording soil gas concentrations and searching for precursor anomalies before strong earthquakes in South Kamchatka

At the Petropavlovsk-Kamchatsky geodynamic test site the instrumental complex has operated for the registration of subsurface gas concentration since 2006. In this paper the main components of the complex and their capabilities are described. To illustrate the work of the complex the dynamics of subsurface gas concentrations in the period from February to March 2011 (before and after the earthquake off the coast of Japan, March 11, 2011, M = 9.0) in one of the registration points was analyzed. These data indicate geodynamic processes during this period in the considered area at the point of subsurface gas registration. Selected dynamics anomalies of the subsurface gas concentrations can be regarded as a short-term remote precursor of the earthquake off the coast of Japan.

The earthquake recurrence law and energy balance of the seismic process

Relationships between the average seismic energy of strong and weak earthquakes in confined ranges are considered. These relationships are related to the earthquake recurrence (Gutenberg-Richter) law parameters. The theoretical foundation of the study is based on the results obtained by M.A. Sadovsky and V.F. Pisarenko in 1999, who described the indicated law as a ratio of the total seismic energy and maximum expected earthquake. Some empirical relationships obtained by the author on the basis of the Kamchatka and Sakhalin regional earthquake catalogs are reported. The determination of the recurrence law parameters on the basis of these relationships is shown to be efficient.

Simulation of Ground Motion from Strong Earthquakes of Kamchatka Region (1992–1993) at Rock and Soil Sites

To estimate the parameters of ground motion in future strong earthquakes, characteristics of radiation and propagation of seismic waves in the Kamchatka region were studied. Regional parameters of radiation and propagation of seismic waves were estimated by comparing simulations of earthquake records with data recorded by stations of the Kamchatka Strong Motion Network. Acceleration time histories of strong earthquakes (Mw = 6.8–7.5, depths 45–55 km) that occurred near the eastern coast of Kamchatka in 1992–1993 were simulated at rock and soil stations located at epicentral distances of 67–195 km. In these calculations, the source spectra and the estimates of frequency-dependent attenuation and geometrical spreading obtained earlier for Kamchatka were used. The local seismic-wave amplification was estimated based on shallow geophysical site investigations and deep crustal seismic explorations, and parameters defining the shapes of the waveforms, the duration, etc. were selected, showing the best-fit to the observations. The estimated parameters of radiation and propagation of seismic waves describe all the studied earthquakes well. Based on the waveforms of the acceleration time histories, models of slip distribution over the fault planes were constructed for the studied earthquakes. Station PET can be considered as a reference rock station having the minimum site effects. The intensity of ground motion at the other studied stations was higher than at PET due to the soil response or other effects, primarily topographic ones. At soil stations INS, AER, and DCH the parameters of soil profiles (homogeneous pyroclastic deposits) were estimated, and nonlinear models of their behavior in the strong motion were constructed. The obtained parameters of radiation and propagation of seismic waves and models of soil behavior can be used for forecasting ground motion in future strong earthquakes in Kamchatka.

Correlation of the anomalies in the electric field and electric conductivity of the lithosphere to earthquakes in Kamchatka

The data of long-term electromagnetic monitoring are used for studying the dynamics of electric conductivity of the medium and the electric field of the terrestrial sources. The electric conductivity of the medium is estimated from the magnetotelluric transfer functions (impedance tensor and telluric tensor). The electric field of terrestrial sources is identified by filtering the variations of the observed electric field of the Earth. The magnetotelluric parameters and the electric field of terrestrial sources feature anomalous changes of supposedly earthquake-related origin. The anomalies associated with the same earthquake are not simultaneous. It is shown that these anomalies are generated by processes occurring at different depths. The strong earthquake is preceded by the appearance of surface anomalies several months before the event and accompanied by a deep coseismic anomaly. The probable nature of the recognized anomalies is discussed.

A diffusion approach to the statistical analysis of Kamchatka Seismicity

A diffusion approach was used to develop a statistical model of seismicity and to analyze Kamchatka earthquakes in order to detect features in the changes that are typical of random walk processes. We proposed a hypothesis of relationships among events and used an energy criterion to decompose the earth-quake catalog into a set of sequences, with each being a Brownian process with definite spatial, temporal, and energy scales. We constructed statistical distributions for these sequences over the number of their terms and total energies, as well as distributions of the sequences over distance, time, and flight times between events. We discuss non-local properties and memory effects in the random walk under different conditions.

Development of near-surface dilatancy zones as a possible cause for seismic emission anomalies before strong earthquakes

Based on mathematical modeling, the paper presents the estimation of the length of dilatancy zones developed near a free surface during the preparation of earthquakes. An algorithm for the calculation of dilatancy zones has been developed and applied for numerical modeling. Estimated examples of the development of near-surface dilatancy zones before the Kamchatka earthquakes with a magnitude M = 6.7–7.8 are given. The results of the numerical experiments under the accepted assumptions solve the problem of the long-range influence of a future earthquake source on a limited remote zone of microseismic information gathering: the model admits the development of near-surface dilatancy zones in the vicinity of a station recording seismic noise that can trigger forerunner anomalies.

Regional differences in the characteristics of seismic wave emission and propagation in Kamchatka and the Northern Caucasus

A very strong difference in accelerograms is dem� onstrated for the typical earthquakes in Kamchatka and the Northern Caucasus related to the differences in the regional characteristics of emission and propa� gation of seismic waves. The strong scatter of peak accelerations and the parameters of oscillation dura� tion does not allow us to apply the simple relations of the correlation between the seismic intensity and peak acceleration over the entire territory of Russia. The duration of oscillations should also be taken into account. Mapping of the seismic intensity in the form of the seismic intensity numbers chart realized in the OSR�97 charts is correct, but in order to construct the zoning charts in peak accelerations, it is necessary to study in detail the regional peculiarities of the emis� sion and propagation of the seismic waves over the entire territory of Russia. The account for the regional peculiarities of the emission and propagation of seismic waves is neces� sary for the construction industry in seismic regions and the study of these peculiarities is important for such a big country as Russia. Accelerograms of earth� quakes can also be different in seismic regions located far from each other, which differ in their geological and tectonic structure. The level of seismic hazard on the territory of the Russian Federation is characterized in the charts of seismic zoning OSR�97�A, B, and C. The charts reflect the seismic intensity, and the probability that it can be exceeded within 50 years is 10% (OSR�97�A), 5% (OSR�97�B), and 1% (OSR�97�C). According to

Patterns in the daily periodicity of low magnitude seismicity in Kamchatka

A daily periodicity in small (K ≤ 8. 0) Kamchatka earthquakes has been detected, with the maximum occurring during the nighttime. The effect was not observed throughout the area of study, but only in several zones. We show that the results are not affected by human and weather factors. A hypothesis is put forward to explain the physical causes of the effect, viz., that the daily periodicity of small earthquakes could be due to natural VLF electromagnetic radiation acting on the geologic medium. It is pointed out that the effect is related to the previously identified effect of natural electromagnetic radiation modulating the intensity of geoacoustic emission from rocks.

Diurnal periodicity of weak earthquakes and high-frequency underground noise in Kamchatka

We have analyzed the data on the times and number of weak earthquakes (M = 0–2.5) included in the up-to-date (final version) Catalog of Kamchatka Earthquakes for 1995–2008, and the intensity of highfrequency underground noise measured in the deep borehole near Petropavlovsk-Kamchatskiy (according to the literature data). We calculated the spectra of the seismic time series within the range of periods from 1 to 48 hours with a step of one minute. It was found that the spectrum of the earthquake data series contains a significant high Q extremum in a period of 24 hours that can be linked with a similar period in the high-frequency underground noise in Kamchatka and in the Russian Platform. There are some grounds to suggest that the weak earthquakes and the underground noise (seismoacoustic emission) have the same nature. In both cases, the shapes of the curve of the diurnal periodicity are found to depend on the duration of light during the day. The probable reasons for the solar impact on the seismic emission processes are discussed.

A probabilistic model of seismicity: Kamchatka earthquakes

The catalog of Kamchatka earthquakes is represented as a probability space of three objects {Ω, \( \tilde F \)P}. Each earthquake is treated as an outcome ωi in the space of elementary events Ω whose cardinality for the period under consideration is given by the number of events. In turn, ωi is characterized by a system of random variables, viz., energy class ki, latitude φi, longitude λi, and depth hi. The time of an outcome has been eliminated from this system in this study. The random variables make up subsets in the set \( \tilde F \) and are defined by multivariate distributions, either by the distribution function \( \tilde F \) (φ, λ, h, k) or by the probability density f(φ, λ, h, k) based on the earthquake catalog in hand. The probabilities P are treated in the frequency interpretation. Taking the example of a recurrence relation (RR) written down in the form of a power law for probability density f(k), where the initial value of the distribution function f(k0) is the basic data [Bogdanov, 2006] rather than the seismic activity A0, we proceed to show that for different intervals of coordinates and time the distribution felim(k) of an earthquake catalog with the aftershocks eliminated is identical to the distribution ffull(k), which corresponds to the full catalog. It follows from our calculations that f0(k) takes on nearly identical numeral values for different initial values of energy class k0 (8 ≤ k0 ≤ 12) f(k0). The difference decreases with an increasing number of events. We put forward the hypothesis that the values of f(k0) tend to cluster around the value 2/3 as the number of events increases. The Kolmogorov test is used to test the hypothesis that statistical recurrence laws are consistent with the analytical form of the probabilistic RR based on a distribution function with the initial value f(k0) = 2/3. We discuss statistical distributions of earthquake hypocenters over depth and the epicenters over various areas for several periods