Seismic Emission Research Articles

The Role of Magnetic Fields in Transient Seismic Emission Driven by Atmospheric Heating in Flares

Transient seismic emission in flares remains largely mysterious. Its discoverers proposed that seismic transients are driven by impulsive heating of the flaring chromosphere. Simulations of such heating show strong shocks, but these are damped by heavy radiative losses as they proceed downward. Because compression of the gas the shock enters both heats it and increases its density, the radiative losses increase radically with the strength of the shock, leaving doubt that sufficient energy can penetrate into the solar interior to explain helioseismic signatures. We note that simulations to date have no account for strong, inclined magnetic fields characteristic of transient-seismic-source environments. A strong horizontal magnetic field, for example, greatly increases the compressional modulus of the chromospheric medium, greatly reducing compression of the gas, hence radiative losses. Inclined magnetic fields, then, must be fundamental to the role of impulsive heating in transient seismic emission.

Statistically-based approach for monitoring of micro-seismic events

We consider the problem of optimal statistical estimation of micro-seismic source parameters using multichannel data from surface arrays of seismometers affected by a strong seismic noise. The problem is treated as a statistical task of parameter estimation for a general type multidimensional linear model with random or completely unknown input time functions. The maximum-likelihood generic estimators are derived and their relationship with the well-known seismic emission tomography (SET) algorithm is established. The proposed estimation algorithms perform processing of multichannel discrete observations in the frequency domain and can be implemented in on-line mode. Using the method of successive independent trials (Monte-Carlo), we demonstrate that a proposed statistical estimation algorithm provides much higher accuracy of the micro-seismic event source location in real noise conditions than the widely used SET algorithm and, as a consequence, is more reliable in practical applications.

Kinetics of seismic emission in coal mines in Kuzbass

The article gives the experimental evidence of effective use of the kinematic criterion χ, derived by Oparin for “apparent” velocities of pendulum waves based on deterministic description of seismic energy release in the Norilsk mine fields, in assessment of stresses and strains in coal beds in terms of the Polysaevskaya Mine, Kuzbass.

Statistics of Local Seismic Emission from the Solar Granulation

We apply computational seismic holography to high-frequency helioseismic observations of the quiet Sun from SDO/HMI to locate predominant sources of seismic emission with respect to the structure of the solar granulation. The regions of greatest seismic emission are the edges of photospheric granules. Seismic emission from regions whose continuum brightnesses are 95–100% of the mean, as resolved by HMI, are about 2.5 times as emissive as regions whose brightnesses are 100-104% of the mean. The greater seismic emissivity from regions whose brightnesses are somewhat less than the mean is roughly in line with expectations from an understanding that attributes most seismic emission to cool plumes plummeting from the edges of granules. However, seismic emission from regions whose continuum brightnesses significantly exceed 104% of the mean is also remarkably high. This unexpected feature of high-frequency seismic emission from the solar granulation begs to be understood.

Enhanced sources of acoustic power surrounding AR 11429

Multi-frequency power maps of the local acoustic oscillations show acoustic enhancements ("acoustic-power halos") at high frequencies surrounding large active region. Computational seismic holography reveals a high-frequency "acoustic-emission halo", or "seismic glory" surrounding large active regions. In this study, we have applied computational seismic holography to map the seismic seismic source density surrounding AR 11429. Studies of HMI/SDO Doppler data, shows that the "acoustic halos" and the "seismic glories" are prominent at high frequencies 5–8 mHz. We investigate morphological properties of acoustic-power and acoustic emission halos around an active region to see if they are spatially correlated. Details about the local magnetic field from vectormagnetograms of AR 11429 are included.We identify a 15" region of seismic deficit power (dark moat) shielding the white-light boundary of the active region. The size of the seismic moat is related to region of intermediate magnetic field strength. The acoustic moat is circled by the halo of enhanced seismic amplitude as well as enhanced seismic emission. Overall, the results suggest that features are related. However, if we narrow the frequency band to 5.5 – 6.5 mHz, we find that the seismic source density dominates over the local acoustic power, suggesting the existence of sources that emit more energy downward into the solar interior than upward toward the solar surface.

Near-field range of the direct-impact seismic source

The authors have developed and numerically analyzed a model of near-field range of the percussion-type well seismic source emission. The obtained estimates of attack energy on productive strata at underspeed seismic waves and varied position of the source relative to the stratum are presented in the article.

Magneto-Acoustic Energetics Study of the Seismically Active Flare of 15 February 2011

Multi--wavelength studies of energetic solar flares with seismic emissions have revealed interesting common features between them. We studied the first GOES X--class flare of the 24th solar cycle, as detected by the Solar Dynamics Observatory (SDO). For context, seismic activity from this flare (SOL2011-02-15T01:55-X2.2, in NOAA AR 11158) has been reported in the literature (Kosovichev, 2011; Zharkov et al., 2011). Based on Dopplergram data from the Helioseismic and Magnetic Imager (HMI), we applied standard methods of local helioseismology in order to identify the seismic sources in this event. RHESSI hard X-ray data are used to check the correlation between the location of the seismic sources and the particle precipitation sites in during the flare. Using HMI magnetogram data, the temporal profile of fluctuations in the photospheric line-of-sight magnetic field is used to estimate the magnetic field change in the region where the seismic signal was observed. This leads to an estimate of the work done by the Lorentz-force transient on the photosphere of the source region. In this instance this is found to be a significant fraction of the acoustic energy in the attendant seismic emission, suggesting that Lorentz forces can contribute significantly to the generation of sunquakes. However, there are regions in which the signature of the Lorentz-force is much stronger, but from which no significant acoustic emission emanates.

Seismoacoustic lunar fields and lunar electromagnetic (nonthermal) emission

For better insight into lunar radio emissions, observations of the Moon were made during the maximal Geminids meteor shower and during the lunar eclipse without external effects. Statistical processing of the obtained data was carried out. It was found that the lunar endogenous and exogenous processes are displayed in both the seismic-emission fields and lunar nonthermal electromagnetic emissions. Both types of signals demonstrate good correlation. The seismic and electromagnetic emission processes have common periodicities, some of which determine the internal structure of the Moon. Similar regularities are expected for other bodies of the Solar System.

The impact of technogenic factors on the seismicity of the Kuznetsk Basin region and Lake Baikal

Using the materials from the catalogue of seismic events in the Siberian region, we estimated the impact of man’s activity on natural seismicity. Local man’s intervention into natural processes has been studied by the examples of commercial explosions during the quarry mineral mining in the Kuznetsk Basin and the exploitation of the railroad site along the shore of Lake Baikal. Seismic emission is shown to change with time under the impact of powerful monochromatic vibrators on the environment.

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.

Comparison of the diurnal periodicity features of seismic noise, earthquakes, and electric power consumption

The main features of periodic changes in the parameters of seismic noise, seismicity and electric power consumption in industrial networks are compared to verify the hypothesis on the technogenic influence of electric network load on seismic noise and seismicity and to search for possible origins of the diurnal periodicity in seismic emission processes discovered in various regions of the world. Sufficiently good similarity of the compared processes is revealed that does not contradict the hypothesis. However, there are also some important discrepancies. An inverse phase pattern of interdiurnal distributions of weak and strong Japanese earthquakes has been found, and various possible mechanisms of this phenomenon, which had been observed earlier in certain other regions, are discussed.

ANATOMY OF A SOLAR FLARE: MEASUREMENTS OF THE 2006 DECEMBER 14 X-CLASS FLARE WITH GONG,HINODE, ANDRHESSI

Some of the most challenging observations to explain in the context of existing flare models are those related to the lower atmosphere and below the solar surface. Such observations, including changes in the photospheric magnetic field and seismic emission, indicate the poorly understood connections between energy release in the corona and its impact in the photosphere and the solar interior. Using data from Hinode, TRACE, RHESSI, and GONG we study the temporal and spatial evolution of the 2006 December 14 X-class flare in the chromosphere, photosphere, and the solar interior. We investigate the connections between the emission at various atmospheric depths, including acoustic signatures obtained by time-distance and holography methods from the GONG data. We report the horizontal displacements observed in the photosphere linked to the timing and locations of the acoustic signatures we believe to be associated with this flare, their vertical and horizontal displacement velocities, and their potential implications for current models of flare dynamics.

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

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.

Stochastic Seismic Emission from Acoustic Glories in Solar Active Regions

Helioseismic images of active regions show enhanced seismic emission in 5 mHz oscillations in a halo surrounding the active region called the "acoustic glory". In this paper we analyse the high-frequency power excess surrounding two active regions that occurred during the "shy" ascending phase of the solar cycle 24, at the beginning of 2010. This study compares the acoustic properties of seismic emission from acoustic glories with that from the quiet Sun. The power distribution of quiet-Sun seismic emission far from solar activity is exponential, as for random Gaussian noise, and therefore not episodic. The magnitudes of the acoustic glories and their seismic structure allow us to make predictions of the seismic behaviour of active regions and compare the data with present theoretical models.

New algorithms of emission tomography for passive seismic monitoring of a producing hydrocarbon deposit: Part II. Results of real data processing

The new suggested algorithms of seismic emission tomography and those used earlier made it possible to dispose of the effects caused by a strong industrial noise, to study the structure of the upper part of the Earth’s crust and to monitor the seismic processes that take place within the oil deposit being developed in West Siberia. An efficient use of the industrial background seismic illumination allowed three-dimensional imaging of the fault zone. From the recorded seismic noise at the time of arrival of the high-amplitude low-frequency seismic wave, a localized soliton-like object floating upwards on the rupture with the velocity of 10 m/s is identified. In the depth range from 1 to 6 km a vertical filament-like seismic source that is hypothesized to be associated with the vortex geological structure, namely, the zone of torsional strains, is revealed. The position of this source in a plane remains stable within 9 days, although the bursts in the amplitude of both industrial and natural seismic radiation affect the depth distribution of the radiation and result in the appearance of additional seismic sources.

New algorithms of emission tomography for passive seismic monitoring of a producing hydrocarbon deposit: Part I. Algorithms of processing and numerical simulation

Two new algorithms of seismic emission tomography and the results of their numerical testing are presented. The algorithms allow eliminating of the screening effect caused by spatially correlated noise, and imaging of deep weak sources. Both algorithms invoke spatial filters, calculated on the basis of singular decomposition of the spectral matrix of the wave field. The key parameter of such a filter is the number of eigenvectors of the spectral matrix, which must be rejected in the process of seismic emission imaging in order to eliminate the screening effect. Consecutive increasing in the number of rejected eigenvectors enables imaging of ever weaker seismic sources.

Resonant seismic emission of subsurface objects

Numerical modeling results and field data indicate that some contrasting subsurface objects (such as tunnels, caves, pipes, filled pits, and fluid-filled fractures) are capable of generating durable resonant oscillations after trapping seismic energy. These oscillations consist of surface types of circumferential waves that repeatedly propagate around the object. The resonant emission of such trapped energy occurs primarily in the form of shear body waves that can be detected by remotely placed receivers. Resonant emission reveals itself in the form of sharp resonant peaks for the late parts of the records, when all strong direct and primary reflected waves are gone. These peaks were observed in field data for a buried barrel filled with water, in 2D finite-difference modeling results, and in the exact canonical solution for a fluid-filled sphere. A computed animation for the diffraction of a plane wave upon a low-velocity elastic sphere confirms the generation of resonances by durable surface waves. Resonant emission has characteristic quasi-hyperbolic traveltime patterns on shot gathers. The inversion of these patterns can be performed in the frequency domain after muting the strong direct and primary scattered waves. Subsurface objects can be detected and imaged at a single resonance frequency without an accurate knowledge of source trigger time. The imaging of subsurface objects requires information about the shear velocity distribution in an embedding medium, which can be done interactively during inversion.

Elimination of high-amplitude noise during passive monitoring of hydrocarbon deposits by the emission tomography method

Emission tomography used in passive seismic monitoring of hydrocarbon deposits enables regular inspection of development of hydraulic fracturing and relaxation processes in volumes of fracturing, tracing of fluid migration paths, redistribution of stresses due to field development accompanied by seismic emission from volumes of structural defects and stress concentration, and localization of fractured and faulted structures from emission and scattering data. Intensive man-made seismic noise in the areas of oil field development produces a strong screening effect in identification of weak deep seismic sources. On the basis of experiments with simulated and real data of surface seismic arrays in regions of oil deposits in Western Siberia (carried out in the framework of the passive monitoring program of the SYNAPSE Science Center), it is shown that the use of algorithms of adaptive optimal and rejection spatial filtering with the estimation of the spectral density matrix of multichannel observations in the framework of multivariate autoregressive-moving average modeling is effective for eliminating the influence of anthropogenic noise and revealing (in oil production areas) both deep seismic sources supposedly active in scattering regions of the lower part of the sedimentary cover and the crystalline basement. The projection of the scattering regions onto the horizontal plane correlates well with the position of faults in the area of in situ observations.

The Mechanisms of Particle Kinetics and Dynamics Leading to Seismic Emission and Sunquakes

In this paper the mechanisms responsible for observational features associated with sunquakes induced by different classes of solar flares are compared. The role of high-energy particle beams via Coulomb and Ohmic heating of the ambient plasma and nonthermal excitation and ionization is explored for different beam parameters at various atmospheric depths. On the one hand, only hard electron beams with high-energy fluxes are found producing extensive nonthermal hydrogen ionization, four orders of magnitude higher than in the quiet atmosphere. This excess ionization leads to the white-light flares associated with the seismic emission appearing simultaneously with hard X-ray emission and, consequently, to a strong increase of Ni-line emission observed as the seismic emission measured with the holographic technique. On the other hand, the ambient plasma hydrodynamic response to heating by such beam electrons forms hydrodynamic shocks just below the transition region, in the upper chromosphere, and they travel with supersonic velocity for up to five minutes before reaching the photosphere. These hydrodynamic responses caused by the beam electrons are maximized in the lower chromosphere for moderate electron beams because of their smaller Ohmic losses in the upper atmosphere compared to those for higher-energy electron beams whose bulk energy is deposited in the transition region. These shocks caused by electron beams can explain the observations of seismic emission by time – distance (TD) diagrams and the holographic method in M- and C-class flares, whereas to account for the quakes in X-class flares, high-energy quasi-thermal protons or power-law proton beams either by themselves or blended with electron beams are the most likely agents. Nonthermal ionization and excitation of lower atmospheric levels during the beam injection followed by thermo-conductive heating after the beam is stopped can contribute to the seismic signatures observed with the holographic technique caused by strong nonthermal ionization and back-warming heating occurring in the shock while it loses its energy by optically-thick radiation in the photospheric lines and continua.