Kamchatka Earthquakes Research Articles

Macroseismic descriptions and parameters of Kamchatka earthquakes that occurred during the preinstrumental period of observation

This paper presents an analysis of the newly acquired macroseismic descriptions of several Kamchatka earthquakes that occurred in the 18th–19th centuries. The available data for two large earthquakes that occurred in 1737 were analyzed to show that even the very numerous descriptions of the October 17, 1737 earthquake are inadequate to determine the basic parameters (epicentral coordinates, magnitude, and epicentral intensity of shaking). The only sources of information on seismic events in Kamchatka for the 18th–19th centuries were reports of explorers, but their presence in the region was episodic and irregular. We therefore believe that the M=5–8.4 earthquakes were much more numerous during this period than indicated in all the published catalogs.

Intermediate-term precursors of large (M ≥ 6.6) Kamchatka earthquakes for the period from 1987 to 2004: A retrospective assessment of their information content for prediction

Data from the literature were used to systematize intermediate-term (with advance times of 1 month to ∼2.5 years) precursors to the M ≥ 6.6 Kamchatka earthquakes of 1987–2004. The precursors were observed as changes in seismological, geodetic, geophysical, water-level, and hydrochemical parameters. Retrospective assessment of the information content in these intermediate-term precursors for earthquake prediction is in progress. The focus was on estimating the occurrence times of various precursors as functions of earthquake parameters (magnitude M, hypocentral distance R, and epicenter location). In the conditions of the Kamchatka observing network, precursors can be identified by a combination of methods, mostly before M ∼ 7 earthquakes or greater south of the Kronotskii Peninsula, for which M/logR ≥ 3. It is shown that the relative proportion of earthquakes for which precursors have been identified in the observations considered here is 0.43–0.86.

Slip Distribution of the 1952 Kamchatka Great Earthquake Based on Near-Field Tsunami Deposits and Historical Records

We explore the magnitude and slip distribution of the 1952 Kamchatka earthquake (Mw 8.8-9.0) using constraints from the 1952 Kamchatka tsunami. Our new field data provide more comprehensive coverage of the near-field tsunami than had been available to date. We examine the effects of internal slip distribution within complex earthquake ruptures on near-field tsunami runup and evaluate some of the limitations of this approach. Our approach compares tsunami-deposit distribution with simulated runup from tsunamis generated by different configurations of seafloor deformation from hypothetical earthquakes resembling that of the 1952 Kamchatka earthquake. We identify areas of high slip because different distributions of seafloor deformation result in variations in tsunami runup in the near field. Mapped deposits and local observations of the 1952 Kamchatka tsunami indicate that near-field runup in central Kamchatka was consistently less than 10 m (averaging 6 m), while south Kamchatka to the northern Kuril Islands had more variability and higher average runup (8 m runup in South Kamchatka and 10 m runup in the northern Kuril Islands). Our simulations show that in order to produce the distribution of runup indicated by tsunami deposits and historical observations, the 1952 earthquake had regions of high slip off the coast of southern Kamchatka, and the location of high slip is shallower in the subduction zone than previously interpreted. Online Material: Sedimentary methodology, model inputs, and simulation results.

The possibility of estimating the coseismic deformation from water level observations in wells

A method for point estimation of coseismic volume deformation from amplitudes of earthquake-induced jumps in the water level and from the tidal sensitivity of the water level is presented. Application of this method is illustrated by six Kamchatka earthquakes of 1997–2004 with Mw = 6.2–7.8 that occurred 128–316 km from the YuZ-5 well. Estimates of coseismic deformation provided by the level gage observations and by the model agree in amplitude and sign. The model reproduces an extended dislocation source in a homogeneous elastic isotropic half-space. Source rupture parameters correspond to focal mechanisms from the CMT international catalog. Consistence in experimental and theoretical estimates of the volume coseismic deformation indicates the high strain-resistance properties of YuZ-5 borehole and the possibility of quantitative estimation of seismotectonic deformation from high-precision water level measurements with time resolution not lower than 10 minutes.

Parameters of Kamchatka seismicity in 2008

Parameters of Kamchatka seismicity in 2008

A comprehensive analysis of Kamchatka seismicity for the period 2005–2007 using the regional catalog

We characterize the Kamchatka seismicity for the period 2005–2007. Regional catalogs of Kamchatka earthquakes were used to develop 2D distributions of parameters of background seismicity. The characteristics we consider include the activity A10, the slope of the recurrence curve γ, the parameters involved in the methods RTL, ΔS, and the “Z-function”, as well as the control of earthquake clustering. We have detected the space-time agreement between the anomalies exhibited by several parameters.

Subduction of the Pacific plate under Kamchatka: Seismic velocity of underthrust

The results of studying the process of underthrusting in the Pacific plate under Kamchatka are presented, and the phenomena associated with this process are described. The seismic component of the velocity of the plate underthrust is estimated on the basis of (1) data from the CMT (Centroid Moment Tensor) catalog and (2) the sequence of the strongest Kamchatka earthquakes. A flat site with a strike azimuth of 217° and a dip angle of 25° located at depths of 30–70 km is assumed to be the interface between the plunging plate and Kamchatka. From CMT focal mechanisms, the underthrust velocity is estimated at V = 0.7 cm/yr for the southern zone (located south of Cape Shipunski) and at V = 1.1 cm/yr for the central zone (from Cape Shipunski to Cape Kronotski). From pairs of the strongest earthquakes that have occurred successively since 1737, the underthrust velocity for the southern zone is estimated at V = 6.6–7.1 cm/yr (from two pairs) and for the central zone, at V = 6.6 cm/yr. The creep portion of the underthrust amounts to 5–15% of the total velocity (the velocity of motion of the Pacific plate is 8 cm/yr).

On the reality of the 56-year cycle and the increased probability of large earthquakes for Petropavlovsk-Kamchatskii during the period 2008–2011 according to lunar cyclicity

A 56-year cyclicity in the occurrence of large Kamchatka earthquakes has been previously detected. This is another manifestation of the tendency for the timing of large Kamchatka earthquakes to be synchronized to the cycles related to the period To of rotation of the lunar nodes found by V.A. Shirokov in 1974. He identified cycles of 18.6 years = To and 6.2 years = To/3, while the period of the 56-year cycle is 3To. The genuineness of that phenomenon had to be revised in connection with the occurrence of a large (Mw = 7.8) earthquake in Kamchatka at the end of 1997, in violation of the 56-year cyclicity. It turned out that, even though the 56-year cycle has become less distinct after the 1997 event, the cyclicity itself has remained statistically significant. A byproduct is an updated forecast of earthquake hazard for Kamchatka. The update is necessary in view of the approaching hazardous period of 2008–2011. It is found that, assuming the validity of these empirical tendencies, the expected rate of large earthquakes off Kamchatka for the period of August 2008 to October 2011 will be four times as high as the long-term mean. We derive the first-ever estimate of future hazard in terms of felt intensity for specified soil conditions (the so-called average soil) at a specified site (the town of Petropavlovsk-Kamchatskii). For these soil conditions, the estimated probability of at least one shock of intensity VII or greater during the period specified above is equal to 0.39 ± 0.15. The expected rate of single events or sets of events with Mw ≥ 7.6 in Kamchatka during this period is 0.76 ± 0.25.

Space-time variations in the parameters of split S waves excited by local earthquakes in southern Kamchatka

An analysis of the distribution of split S-wave parameters due to small local earthquakes occurring down to a depth of 200 km beneath the PET IRIS station (in the town of Petropavlovsk-Kamchatskii) for the period 1993–2002 revealed an inhomogeneous distribution of anisotropic properties and time-dependent changes in the state of stress and strain in the sinking slab. Three time intervals have been identified from the behavior of the split-wave parameters: 1993–1995, 1996–1998, and 1999–2002. The most orderly orientation of fast-wave polarization azimuths at all depths and lower stresses in the earth was observed in 1996–1998. Regions of relatively stable and unstable parameter behavior consistent with increased and decreased P and S velocities have been identified. The central block down to a depth of 120 km and the lower part of the Benioff zone are classified as stable regions dominated by E-SE fast-wave azimuths. Unstable behavior of fast-wave azimuths was noticed for depths of 60 to 90 km and around the top of the Benioff zone. The highest values of S-wave delay time and regions where the delay times were migrating mostly occur at contacts between more rigid and weakened blocks.

Precursors of large Kamchatka earthquakes based on monitoring of seismic noise

This paper presents results from a monitoring study in high frequency seismic noise in Kamchatka during 1992–2006 and reports their use for predicting large regional earthquakes (M ≥ 6.0) in an epicentral distance range Δ within 400 km. The prediction is based on an original method using earth tides as the standard external excitation to study patterns of seismic emission. The method as used at present is described in detail. Guidelines are delineated for future refinement of the prediction method.

Asymmetrical pulses, the periodicity and synchronization of low frequency microseisms

Seismic records of eight IRIS broadband stations were analyzed at distances of 70 to 7160 km from the magnitude 8.3 Hokkaido earthquake of September 25, 2003. The stations situated in the subduction zone recorded asymmetrical microseismic pulses lasting 3–10 min a few days before the earthquake. No such pulses were observed in the records of the stations situated outside the subduction zone. Similar pulses were also recorded before the magnitude 7.8 Kronotskii, Kamchatka earthquake of 1997. The pulses are hypothesized to have been caused by creeping movements. Synchronous oscillations of microseismic noise with periods of 1–3 h were recorded as far as 3000 km from the Hokkaido earthquake a few days before it occurred. The noise coherence measure increased for stations closer to the epicenter. The question of the source of this coherence remains open. These effects belong to the class of those occurring in dissipative metastable systems; parts of the terrestrial lithosphere during the precursory periods of seismic catastrophes seem to be such systems.

Determination of source parameters of strong earthquakes of Kamchatka, the Kurile Islands, and Japan from aftershock sequences

Aftershock sequences of some strong earthquakes of Kamchatka, the Kurile Islands, and Japan are examined. Such source parameters as the length L, along-dip width W, motion on fault D, and stress drop Δσ are determined from the aftershock sequences considered. The values of these parameters were obtained by the formal estimation of linear source parameters (lower bound estimates) and visually (upper bound estimates). The correlation dependences of the obtained parameters on the surface wave (MS) and seismic moment (MW) magnitudes are calculated.

Intrinsic attenuation and scattering of shear waves in the lithosphere of Kamchatka

Records of small local Kamchatka earthquakes were processed using Multiple Lapse Time Window Analysis (MLTWA). The method makes use of normalized integrals of 3D seismic energy density in several windows applied to an earthquake record that has been put through a bandpass filter. The intrinsic attenuation and scattering properties of the earth were estimated by choosing parameters that provide the best agreement between experimental and theoretical integrals as functions of hypocentral distance. The theoretical normalized integrals as functions of distance were computed using an analytical solution to the equation of seismic energy transport based on a simple model of isotropic scattering for scalar seismic waves excited by an impulse point source in an earth that is uniform as to scattering and intrinsic attenuation. The resulting estimates of attenuation and scattering parameters are similar to those derived in other studies of Kamchatka, as well as of other continents: America (California, US), Europe (the Canary Is., Spain, and Italy), and Asia (Japan).

Prediction of strong earthquakes with the use of the scalar product of matrices with a sliding window

The paper is devoted to the important problem of predicting strong earthquakes in space and time. The solution is based on the hypothesis that the prehistory of strong earthquakes in some region implicates a complex sequence of previous moderate-power earthquakes that is certain to considerable extent and common for various strong earthquakes in this region. The algorithm for finding this commonality is implemented by means of procedures on Boolean matrices with a sliding window and has been approved for the earthquakes in Kamchatka and the Kuril Islands. Sliding examination neatly reveals almost all strong earthquakes that have a long enough prehistory (12 years). It is interesting that such earthquakes are predicted several years prior to the catastrophe with an accuracy of 1 or 2 days in time and 100 km in space. There are no false maxima.

Groundwater chemical anomalies connected with the Kamchatka earthquake (M=7.1) on March 1992

Abstract. The energy released by the earthquakes occurred in the seismogenetic area of the southern Kamchatka (Russia) from January 1977 to December 2004, reveals an increase in the peak energy in the period 1992–1999. This increase is related to the occurrence of seven earthquakes with magnitude ranging from 6.9 to 7.7; the first of these earthquakes happened on 2 March 1992 with M=7.1. For many years, hydro-geochemical data have been collected with a mean sampling rate of three days, in the form of the most common ions and gases in the water of deep wells and natural springs of a network operating in the south area of the Kamchatka, where the capital city Petropavlovsk is located. The collected data were analysed and differences in the trend and in the spectral content of some hydro-geochemical parameters at the springs were pointed out before and after the occurrence of the March 1992 earthquake, indicating clear post-seismic effects. Then an evident increase in the Carbon Dioxide and in the Hydrogen content appeared practically at each measurement site during the two-four years preceding the earthquake, so that long term precursors can be claimed. Finally, an anomalous decrease in the Carbon Dioxide content at the springs was revealed two/three months prior the earthquake, as a middle term precursor. The earthquake on March 1992 was the event nearest (90–120 km) to the measurement sites that happened in last thirty years.

A study of atmospheric influence from earthquake statistics

We analyze daily variation in earthquake (EQ) occurrence to try to find a correlation with atmospheric tide whose basic period is 24 h exactly. In selection of earthquake ensembles we use a specially developed index of seismic activity. In this way we present statistics of earthquakes in Kamchatka during the last 40 years, in Japan during the last 7 years and in California during the last 72 years, which shows a weak but recognizable effect. We explain it by tidal modulation of the earthquake instability process.

Spatial relation between source regions of strong earthquakes (M ≥ 7) on Southern Kamchatka and the distribution of velocities and elastic moduli in the Benioff zone

The presence of a phenomenological relationship between high velocity regions in the Benioff zone and sources of relatively strong earthquakes (M ≥ 6) was established for the first time from the comparison of such earthquakes with the velocity structure of central Kamchatka in the early 1970s. It was found that, in the region with P wave velocities of 8.1–8.5 km/s, the number of M ≥ 6 earthquakes over 1926–1965 was 2.5 times greater than their number in the region with velocities of 7.5–8.0 km/s. Later (in 1979), within the southern Kurile area, Sakhalin seismologists established that regions with VP = 7.3–7.7 km/s are associated with source zones of M = 7.0–7.6 earthquakes and regions with VP = 8.1–8.4 km/s are associated with M = 7.9–8.4 earthquakes. In light of these facts, we compared the positions of M = 7.0–7.4 earthquake sources in the Benioff zone of southern Kamchatka over the period 1907–1993 with the distribution of regions of high P velocities (8.0–8.5 to 8.5–9.0 km/s) derived from the interpretation of arrival time residuals at the Shipunskii station from numerous weak earthquakes in this zone (more than 2200 events of M = 2.3–4.9) over the period 1983–1995. This comparison is possible only in the case of long-term stability of the velocity field within the Benioff zone. This stability is confirmed by the relationship between velocity parameters and tectonics in the southern part of the Kurile arc, where island blocks are confined to high velocity regions in the Benioff zone and the straits between islands are confined to low velocity regions. The sources of southern Kamchatka earthquakes with M = 7.0–7.4, which are not the strongest events, are located predominantly within high velocity regions and at their boundaries with low velocity regions; i.e., the tendency previously established for the strongest earthquakes of the southern Kuriles and central Kamchatka is confirmed. However, to demonstrate more definitely their association with regions of high P wave velocities, a larger statistics of such earthquakes is required. On the basis of a direct correlation between P wave velocities and densities, the distributions of density, bulk modulus K, and shear modulus μ in the upper mantle of the Benioff zone of southern Kamchatka are obtained for the first time. Estimated densities vary from 3.6–3.9 g/cm3 in regions of high VP values to 3.0–3.2 g/cm3 for regions of low VP values. The bulk modulus K in the same velocity regions varies from (1.4–1.8) × 1012 to (0.8–1.1) × 1012 dyn/cm2, respectively, and the shear modulus μ varies from (0.8–1.0) × 1012 to (0.5–0.7) × 1012 dyn/cm2, respectively. Examination of the spatial correlation of the source areas of southern Kamchatka M = 7.0–7.4 earthquakes with the distribution of elastic moduli in the Benioff zone failed to reveal any relationship between their magnitudes and the moduli because of the insufficient statistics of the earthquakes used.

Tikhonov's regularization for deconvolution in the empirical Green function method and vertical directivity effect

Application of Tikhonov's technique, using input errors for the parameter of regularization estimation, enhances the accuracy and stability of the reconstruction of a source time function (STF) by the empirical Green function (EGF) method that gives us an opportunity to use simultaneously for analysis body and surface waves data, and to estimate the horizontal and vertical directivity effects. Knowledge of the last is particularly useful for the choice of an active nodal plane of earthquakes with the dip slip fault orientation that allows us to classify these earthquakes to the interplate or intraplate types and thereby to reach the better understanding of tectonic processes in the region of interest. By way of illustration, an attempt to estimate average parameters of faulting in a first approximation is made herein for two Russian Far East large events with opposite types of focal mechanism orientation, strike slip and dip slip. The former is not a matter of interest in the context of vertical directivity effect but enables us to test the method. The directivity analysis of pulse durations and inverse amplitudes of the relative source time functions (RSTFs) restored at eight globally distributed stations IRIS indicates that the destruction in the source of the Neftegorsk earthquake (05/27/1995 M W=7.1) propagated roughly horizontally in the direction 8±11° during 19.2±0.4 s along the rupture extending 35.5±4.9 km. The calculated slip distribution along the rupture coincides within the error with the results of field geological measurements on the causal surface fault that proves that the Neftegorsk earthquake source is well described by the model of the linear unilateral fault and gives a good assessment of the method applied. The average parameters of faulting in the Kamchatka earthquake (03/08/1999 M W=6.9) have been determined from data of 13 station IRIS. It was shown that the destruction in its source propagated downward at an angle of about 60° with horizon, in the direction about S156° E, during 13.4±0.2 s, along the rupture totaling 25.5±2.3 km in length. Therefore, the nodal plane, steeply dipped to the SE, was active and this event can be regarded as an intraplate type. Two asperities can be selected; the first with the maximum slip 3.3 m located at a distance of about 7 km from the onset of rupture, and the second with the maximum slip about 0.9 m centered at approximately 19 km from that.

Modal structure of earth-like planets in the presence of magnetic field

Free oscillations of the earth received much attention by the pioneering work of Benioff (1954). He observed an oscillation period of 57 minutes by investigating the data of Kamchatka earthquake and assumed the free oscillations of the earth as its origin. Since then many aspects of the problem has been investigated by different authors.

The Duration-distance Relationship and Average Envelope Shapes of Small Kamchatka Earthquakes

Average envelope shapes (mean square amplitude time histories) of small earthquakes represent a convenient basis for the construction of semi-empirical stochastic ''Green's functions,'' needed for prediction of future strong ground motion. At the same time, they provide crucial evidence for verification of the theories of scattering of high-frequency seismic waves in the lithosphere. To determine such shapes in the Kamchatka region we use the records of near (R = 50-200 km) shallow earthquakes located around the broadband station PET. On these records, we select the S-wave group and determine its root-mean-square duration Trms, separately for each of the five octave frequency bands. We determine the empirical Trms vs. distance dependence and find it to be very close to a linear one. At the reference distance R = 100 km, average Trms decreases from 5.4 sec for the 0.75 Hz band to 3.9 sec for the 12 Hz band. To analyze average envelopes, we assume that the functional form of the envelope shape function is independent of distance, and stretch each of the observed envelopes along the time axis so as to reduce it to a fixed distance. Through averaging of these envelopes we obtain characteristic envelope shape functions. We qualitatively analyze these shapes and find that around the peak they are close to the shapes expected for a medium with power-law inhomogeneity spectrum, with the spectral exponent 3.5-4. From onset-to- peak delay times we derive the values of transport mean free path and of scattering Q for a set of distances.