scholarly journals Specific features of earth’s free oscillations after deep-focus sea of Okhotsk earthquake of May 24, 2013

2019 ◽  
Vol 488 (6) ◽  
pp. 651-654
Author(s):  
I. P. Kuzin ◽  
L. I. Lobkovsky ◽  
K. A. Dozorova
Keyword(s):  
Sea Of Okhotsk ◽  
Strong Earthquake ◽  
Strain Energy ◽  
P Wave ◽  
Free Oscillations ◽  
P Waves ◽  
Initial Excitation ◽  
Earth’S Free Oscillations ◽  
New Interpretation ◽  
Deep Focus

A description of initial excitation of spheroidal mode 0S2 initiated by the 2013 Sea of Okhotsk earthquake (Mw= 8.3) is presented. It is based on newly revealed fact of standing P-wave origination in the epicenter of the Sea of Okhotsk earthquake and excitation of traveling surface P-waves on the Earths surface by this wave. A new interpretation of the nature of free spheroidal Earths oscillations in case of strong earthquake (М 7,5) is proposed. The spheroidal mode 0S2 is interpreted as combination of standing and traveling P-waves, transferring the Earths strain energy.

scholarly journals Okhotsk deep earthquake 24.05.2013: nature of coseismal earth’s oscillations and estimation of P-wave amplitudes at teleseismic distances

2019 ◽  
Vol 486 (2) ◽  
pp. 237-242
Author(s):  
I. P. Kuzin ◽  
L. I. Lobkovskiy ◽  
K. A. Dozorova
Keyword(s):  
Sea Of Okhotsk ◽  
Seismic Waves ◽  
P Wave ◽  
P Waves ◽  
Deep Earthquake ◽  
Epicentral Area ◽  
Seismic Stations ◽  
The Sea Of Okhotsk ◽  
Gps Observations

The results of coseismic GPS observations in the epicentral area of 2013 Sea-of- Okhotsk earthquake are presented and specific features of seismic waves amplitudes variations with distance are detected basing on the records of Russian and international seismic stations. Global propagation of P-waves for the Sea-of-Okhotsk and Bolivian (09.06.1994) earthquakes was studied and their amplitudes on teleseismic distances were estimated.

scholarly journals Comparison of fluid tiltmeter data with long-period seismograms: Surface waves and Earth's free oscillations

2006 ◽  
Vol 111 (B11) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. M. G. Ferreira ◽  
N. F. d'Oreye ◽  
J. H. Woodhouse ◽  
W. Zürn
Keyword(s):  
Surface Waves ◽  
Free Oscillations ◽  
Long Period ◽  
Earth’S Free Oscillations

Simulation of thermoelastic waves based on the Lord-Shulman theory

Geophysics ◽  
2021 ◽  
Vol 86 (3) ◽  
pp. T155-T164
Author(s):  
Wanting Hou ◽  
Li-Yun Fu ◽  
José M. Carcione ◽  
Zhiwei Wang ◽  
Jia Wei
Keyword(s):  
Thermal Conductivity ◽  
Expansion Coefficient ◽  
Velocity Dispersion ◽  
Wave Attenuation ◽  
Splitting Method ◽  
Grazing Incidence ◽  
P Wave ◽  
Staggered Grid ◽  
Thermal Mode ◽  
P Waves

Thermoelasticity is important in seismic propagation due to the effects related to wave attenuation and velocity dispersion. We have applied a novel finite-difference (FD) solver of the Lord-Shulman thermoelasticity equations to compute synthetic seismograms that include the effects of the thermal properties (expansion coefficient, thermal conductivity, and specific heat) compared with the classic forward-modeling codes. We use a time splitting method because the presence of a slow quasistatic mode (the thermal mode) makes the differential equations stiff and unstable for explicit time-stepping methods. The spatial derivatives are computed with a rotated staggered-grid FD method, and an unsplit convolutional perfectly matched layer is used to absorb the waves at the boundaries, with an optimal performance at the grazing incidence. The stability condition of the modeling algorithm is examined. The numerical experiments illustrate the effects of the thermoelasticity properties on the attenuation of the fast P-wave (or E-wave) and the slow thermal P-wave (or T-wave). These propagation modes have characteristics similar to the fast and slow P-waves of poroelasticity, respectively. The thermal expansion coefficient has a significant effect on the velocity dispersion and attenuation of the elastic waves, and the thermal conductivity affects the relaxation time of the thermal diffusion process, with the T mode becoming wave-like at high thermal conductivities and high frequencies.

Estimates of velocity structure and source depth using multiple P waves from aftershocks of the 1987 Elmore Ranch and Superstition Hills, California, earthquakes

1991 ◽  
Vol 81 (2) ◽  
pp. 508-523
Author(s):  
Jim Mori
Keyword(s):  
Velocity Structure ◽  
Velocity Model ◽  
P Wave ◽  
Sediment Layer ◽  
Source Depth ◽  
Imperial Valley ◽  
P Waves ◽  
Main Shocks ◽  
Aftershock Sequences ◽  
Event Record

Abstract Event record sections, which are constructed by plotting seismograms from many closely spaced earthquakes recorded on a few stations, show multiple free-surface reflections (PP, PPP, PPPP) of the P wave in the Imperial Valley, California. The relative timing of these arrivals is used to estimate the strength of the P-wave velocity gradient within the upper 5 km of the sediment layer. Consistent with previous studies, a velocity model with a value of 1.8 km/sec at the surface increasing linearly to 5.8 km/sec at a depth of 5.5 km fits the data well. The relative amplitudes of the P and PP arrivals are used to estimate the source depth for the aftershock distributions of the Elmore Ranch and Superstition Hills main shocks. Although the depth determination has large uncertainties, both the Elmore Ranch and Superstition Hills aftershock sequences appear to have similar depth distribution in the range of 4 to 10 km.

Reflection moveout approximations for P-waves in a moderately anisotropic homogeneous tilted transverse isotropy layer

Geophysics ◽  
2017 ◽  
Vol 82 (5) ◽  
pp. C175-C185 ◽  
Author(s):  
Ivan Pšenčík ◽  
Véronique Farra
Keyword(s):  
Transverse Isotropy ◽  
Transversely Isotropic ◽  
P Wave ◽  
Weak Anisotropy ◽  
P Waves ◽  
3D Space ◽  
Axis Of Symmetry ◽  
Relative Errors ◽  
Symmetry Tests ◽  
Ti Media

We have developed approximate nonhyperbolic P-wave moveout formulas applicable to weakly or moderately anisotropic media of arbitrary anisotropy symmetry and orientation. Instead of the commonly used Taylor expansion of the square of the reflection traveltime in terms of the square of the offset, we expand the square of the reflection traveltime in terms of weak-anisotropy (WA) parameters. No acoustic approximation is used. We specify the formulas designed for anisotropy of arbitrary symmetry for the transversely isotropic (TI) media with the axis of symmetry oriented arbitrarily in the 3D space. Resulting formulas depend on three P-wave WA parameters specifying the TI symmetry and two angles specifying the orientation of the axis of symmetry. Tests of the accuracy of the more accurate of the approximate formulas indicate that maximum relative errors do not exceed 0.3% or 2.5% for weak or moderate P-wave anisotropy, respectively.

scholarly journals Physiological ECG Value for Polish Half-Bred Anglo-Arab Horses

2012 ◽  
Vol 56 (4) ◽  
pp. 631-635 ◽  
Keyword(s):  
Heart Rate ◽  
P Wave ◽  
P Waves ◽  
T Wave ◽  
Duration Time ◽  
Qt Intervals ◽  
Electrocardiographic Examination ◽  
Electrocardiographic Findings ◽  
Almost All ◽  
T Waves

Abstract The electrocardiographic examination was performed in 33 training horses (2-16 years of age, 11 males and 22 females). Einthoven and precordial leads (I, II, III, aVR, aVL, aVF, CV1, CV2, CV4) were used. The ECG was performed in resting horses and immediately after exercise (10 min walk, 15 min trot, 10 min canter) using a portable Schiller AT-1 3-channel electrocardiograph, with a paper speed of 25 mm sec-1 and a sensitivity of 10 mm.mV-1. The heart rate, wave amplitudes, and duration time were estimated manually. All horses presented a significant increase in heart rate after exercise (rest 43.83 ±10.33 vs. exercise 73.2 ±14.8). QT intervals were significantly shortened in most of the leads. In resting horses, all P waves in the lead I were positive and almost all II, III and CV4 leads were positive. Simple negative P wave dominated in aVR and only simple negative T wave was found in the leads I. The biphasic shape was observed. After exercise, the amplitude of P and T waves rose, however, clear changes were not observed in wave polarisation and form. In the absence of specific racial characteristics of the electrocardiogram in the Polish Anglo- Arabians, electrocardiographic findings can be interpreted according to ECG standards adopted for horses.

scholarly journals Beat-to-Beat P-Wave Analysis Outperforms Conventional P-Wave Indices in Identifying Patients with a History of Paroxysmal Atrial Fibrillation during Sinus Rhythm

Diagnostics ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1694
Author(s):  
Dimitrios Tachmatzidis ◽  
Dimitrios Filos ◽  
Ioanna Chouvarda ◽  
Anastasios Tsarouchas ◽  
Dimitrios Mouselimis ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Paroxysmal Atrial Fibrillation ◽  
Univariate Analysis ◽  
Multivariate Logistic Regression Analysis ◽  
P Wave ◽  
P Value ◽  
Wave Analysis ◽  
P Waves ◽  
History Of

Early identification of patients at risk for paroxysmal atrial fibrillation (PAF) is essential to attain optimal treatment and a favorable prognosis. We compared the performance of a beat-to-beat (B2B) P-wave analysis with that of standard P-wave indices (SPWIs) in identifying patients prone to PAF. To this end, 12-lead ECG and 10 min vectorcardiogram (VCG) recordings were obtained from 33 consecutive, antiarrhythmic therapy naïve patients, with a short history of low burden PAF, and from 56 age- and sex-matched individuals with no AF history. For both groups, SPWIs were calculated, while the VCG recordings were analyzed on a B2B basis, and the P-waves were classified to a primary or secondary morphology. Wavelet transform was used to further analyze P-wave signals of main morphology. Univariate analysis revealed that none of the SPWIs performed acceptably in PAF detection, while five B2B features reached an AUC above 0.7. Moreover, multivariate logistic regression analysis was used to develop two classifiers—one based on B2B analysis derived features and one using only SPWIs. The B2B classifier was found to be superior to SPWIs classifier; B2B AUC: 0.849 (0.754–0.917) vs. SPWIs AUC: 0.721 (0.613–0.813), p value: 0.041. Therefore, in the studied population, the proposed B2B P-wave analysis outperforms SPWIs in detecting patients with PAF while in sinus rhythm. This can be used in further clinical trials regarding the prognosis of such patients.

scholarly journals P- waves reflected from the "20" discontinuity" beneath the Mediterranean region

2010 ◽  
Vol 28 (1) ◽  
Author(s):  
A BOTTARI ◽  
B. FEDERICO
Keyword(s):  
Mediterranean Area ◽  
P Wave ◽  
Travel Times ◽  
P Waves ◽  
First Order ◽  
P Wave Velocity ◽  
Different Depths ◽  
The Mediterranean ◽  
Regional Character ◽  
Order Discontinuity

The observed travel-times of the P-waves for twenty shallow, intermediate, and deep earthquakes, with epicenters in the Mediterranean area, are used in order to analyze some characteristics of the upper mantle. A first- order discontinuity, identifiable as the "20° discontinuity", is found at a depth of 505 ± 16 km in the area underneath the Mediterranean basin. The velocity contrast is equal to 12% (above T'= 8.9 km/sec; below V= 9.97 km/sec). Assuming that this discontinuity gives rise to reflected P-waves (PdP), the travel times of these waves are calculated for various hypocentral depths. The observation of impulses identified as PdP on the seismograms of Messina supports this hypothesis. This result and its implications are discussed in the contest of the conclusions of various authors who locate a P-wave velocity-discontinuity at different depths between 400 and 580 km. Finally, particular emphasis is given to the regional character of the analyzed structures in question.

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