Fault parameters determined by near- and far-field data: The Wakasa Bay earthquake of March 26, 1963

1974 ◽  
Vol 64 (5) ◽  
pp. 1369-1382 ◽  
Author(s):  
Katsuyuki Abe
Keyword(s):  
Effective Stress ◽  
Stress Drop ◽  
P Wave ◽  
Slip Angle ◽  
Polarization Angle ◽  
S Wave ◽  
Seismological Data ◽  
Fault Parameters ◽  
Wakasa Bay ◽  
Dip Angle

Abstract The source process of the Wakasa Bay earthquake (M = 6.9, 35.80°N, 135.76°E, depth 4 km) which occurred near the west coast of Honshu Island, Japan, on March 26, 1963, is studied on the basis of the seismological data. Dynamic and static parameters of the faulting are determined by directly comparing synthetic seismograms with observed seismograms recorded at seismic near and far distances. The De Hoop-Haskell method is used for the synthesis. The average dislocation is determined to be 60 cm. The overall dislocation velocity is estimated to be 30 cm/sec, the rise time of the slip dislocation being determined as 2 sec. The other fault parameters determined, with supplementary data on the P-wave first motion, the S-wave polarization angle, and the aftershocks, are: source geometry, dip direction N 144°E, dip angle 68°, slip angle 22° (right-lateral strike-slip motion with some dip-slip component); fault dimension, 20 km length by 8 km width; rupture velocity, 2.3 km/sec (bilateral); seismic moment, 3.3 × 1025 dyne-cm; stress drop, 32 bars. The effective stress available to accelerate the fault motion is estimated to be about 40 bars. The approximate agreement between the effective stress and the stress drop suggests that most of the effective stress was released at the time of the earthquake.

Source dynamics of the Dasht-e Bayāz earthquake of August 31, 1968

1969 ◽  
Vol 59 (5) ◽  
pp. 1843-1861
Author(s):  
Mansour Niazi
Keyword(s):  
Stress Drop ◽  
Main Shock ◽  
Mean Value ◽  
The Body ◽  
P Wave ◽  
Polarization Angle ◽  
S Wave ◽  
Long Duration ◽  
First Motion ◽  
Complicated Pattern

abstract Radiation patterns of the P-wave first motion and S-wave polarization angle of the Dasht-e Bayāz earthquake of August 31, 1968, as well as its principal aftershock which occurred about 20 hours after the main shock are studied. The main shock data are consistent with the observed left-lateral strike-slip fault which accompanied it. The radiation pattern of the aftershock differs somewhat from that of the main shock and agrees with the directions of the secondary faulting in the area. Several lines of evidence pointing to a multiple source for the main shock are presented. They include complexity of the body phases, low value of the rupture speed as studied from the analysis of the surface wave spectra, reported long duration of shaking and complicated pattern of striations produced by faulting. Energy, moment and stress drop associated with the main shock are estimated. The resulting mean value of stress drop over the faulted surface has a range of 40-100 bars. Based on the age of some well-built structures in the area, it is proposed that no earthquake as severe as the recent one has occurred near the location of the August 31, 1968 earthquake during the last 800 years.

Source mechanism and surface-wave attenuation studies for Tibet earthquake of July 14, 1973

1979 ◽  
Vol 69 (3) ◽  
pp. 737-750
Author(s):  
D. D. Singh ◽  
Harsh K. Gupta
Keyword(s):  
Surface Wave ◽  
Stress Drop ◽  
Wave Attenuation ◽  
Source Parameters ◽  
High Stress ◽  
The Body ◽  
P Wave ◽  
Slip Angle ◽  
Apparent Stress ◽  
Crust And Upper Mantle

abstract Focal mechanism for Tibet earthquake of July 14, 1973 (M = 6.9, mb = 6.0) has been determined using the P-wave first motions, S-wave polarization angles, and surface-wave spectral data. A normal faulting is obtained with a plane having strike N3°W, dip 51°W, and slip angle 81°. The source parameters have been estimated for this event using the body- and surface-wave spectra. The seismic moment, fault length, apparent stress, stress drop, seismic energy release, average dislocation, and fault area are estimated to be 2.96 × 1026 dyne-cm, 27.4 km, 14 bars, 51 bars, 1.4 × 1022 ergs, 157 cm, and 628 km2, respectively. The high stress drop and apparent stress associated with this earthquake indicate that the high stresses are prevailing in this region. The specific quality factor Q is found to vary from 21 to 1162 and 22 to 1110 for Rayleigh and Love waves, respectively. These wide ranges of variation in the attenuation data may be due to the presence of heterogeneity in the crust and upper mantle.

Hypocenter Analysis of Aftershocks Data of the Mw 6.3, 27 May 2006 Yogyakarta Earthquake Using Oct-Tree Importance Sampling Method

2018 ◽  
Vol 881 ◽  
pp. 89-97 ◽  
Author(s):  
Asri Wulandari ◽  
Ade Anggraini ◽  
Wiwit Suryanto
Keyword(s):  
Importance Sampling ◽  
Sampling Method ◽  
Velocity Model ◽  
Fault Scarp ◽  
P Wave ◽  
Double Difference ◽  
S Wave ◽  
Maximum Probability ◽  
Importance Sampling Method ◽  
Dip Angle

Yogyakarta earthquake, Mw 6.3, 27 May 2006 had killed 5,571 victims and destroyed more than 1 million buildings. This incident became the most destructive earthquake disaster over the last 11 years in Indonesia. Earthquake mitigation plan in the area has been carried out by understands the location of the fault. The location of the fault is still unclear among geoscientists until now. In this case, analysis of the aftershocks using oct-tree importance sampling method was applied to support the location of the fault that responsible for the 2006 Yogyakarta earthquake. Oct-tree importance sampling is a method that is recursively subdividing the solution domain into exactly eight children for estimating properties of a particular distribution. The final result of the subdividing process is a cell that has a maximum Probability Density Function (PDF) and identified as the location of the hypocenter. Input data consists of the arrival time of the P wave and S wave of the aftershocks catalog from 3-7 June 2006 and the coordinate of the 12 seismometers, and 1D velocity model of the study area. Based on the hypocenter distribution of the aftershocks data with the proposed method show a clearer trend of the fault compared with the aftershocks distribution calculated with theHypo71program. The fault trend has a strike orientation of N 42° E with a dip angle of 80° parallel with the fault scarp along the Opak River at the distance of about 15 km to the east. This fault trend is similar with the fault orientation obtained using the Double Difference Algorithm.

scholarly journals Petrophysical constraints on the seismic properties of the Kaapvaal craton mantle root

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 45-63 ◽  
Author(s):  
V. Baptiste ◽  
A. Tommasi
Keyword(s):  
Seismic Anisotropy ◽  
Azimuthal Anisotropy ◽  
Mantle Xenoliths ◽  
P Wave ◽  
Kaapvaal Craton ◽  
Compositional Heterogeneity ◽  
S Wave ◽  
Seismic Properties ◽  
Seismological Data ◽  
Cratonic Mantle

Abstract. We calculated the seismic properties of 47 mantle xenoliths from 9 kimberlitic pipes in the Kaapvaal craton based on their modal composition, the crystal-preferred orientations (CPO) of olivine, ortho- and clinopyroxene, and garnet, the Fe content of olivine, and the pressures and temperatures at which the rocks were equilibrated. These data allow constraining the variation of seismic anisotropy and velocities within the cratonic mantle. The fastest P and S2 wave propagation directions and the polarization of fast split shear waves (S1) are always subparallel to olivine [100] axes of maximum concentration, which marks the lineation (fossil flow direction). Seismic anisotropy is higher for high olivine contents and stronger CPO. Maximum P wave azimuthal anisotropy (AVp) ranges between 2.5 and 10.2% and the maximum S wave polarization anisotropy (AVs), between 2.7 and 8%. Changes in olivine CPO symmetry result in minor variations in the seismic anisotropy patterns, mainly in the apparent isotropy directions for shear wave splitting. Seismic properties averaged over 20 km-thick depth sections are, therefore, very homogeneous. Based on these data, we predict the anisotropy that would be measured by SKS, Rayleigh (SV) and Love (SH) waves for five endmember orientations of the foliation and lineation. Comparison to seismic anisotropy data from the Kaapvaal shows that the coherent fast directions, but low delay times imaged by SKS studies, and the low azimuthal anisotropy with with the horizontally polarized S waves (SH) faster than the vertically polarized S wave (SV) measured using surface waves are best explained by homogeneously dipping (45°) foliations and lineations in the cratonic mantle lithosphere. Laterally or vertically varying foliation and lineation orientations with a dominantly NW–SE trend might also explain the low measured anisotropies, but this model should also result in backazimuthal variability of the SKS splitting data, not reported in the seismological data. The strong compositional heterogeneity of the Kaapvaal peridotite xenoliths results in up to 3% variation in density and in up to 2.3% variation of Vp, Vs, and Vp / Vs ratio. Fe depletion by melt extraction increases Vp and Vs, but decreases the Vp / Vs ratio and density. Orthopyroxene enrichment due to metasomatism decreases the density and Vp, strongly reducing the Vp / Vs ratio. Garnet enrichment, which was also attributed to metasomatism, increases the density, and in a lesser extent Vp and the Vp / Vs ratio. Comparison of density and seismic velocity profiles calculated using the xenoliths' compositions and equilibration conditions to seismological data in the Kaapvaal highlights that (i) the thickness of the craton is underestimated in some seismic studies and reaches at least 180 km, (ii) the deep sheared peridotites represent very local modifications caused and oversampled by kimberlites, and (iii) seismological models probably underestimate the compositional heterogeneity in the Kaapvaal mantle root, which occurs at a scale much smaller than the one that may be sampled seismologically.

Azimuthal AVO for tilted TI medium

Geophysics ◽  
2017 ◽  
Vol 82 (1) ◽  
pp. C21-C33 ◽  
Author(s):  
Hongwei Wang ◽  
Suping Peng ◽  
Wenfeng Du
Keyword(s):  
Isotropic Medium ◽  
Symmetry Axis ◽  
Transversely Isotropic ◽  
P Wave ◽  
S Wave ◽  
Transverse Waves ◽  
Propagation Angle ◽  
S Waves ◽  
The Difference ◽  
Dip Angle

With the incident P-wave, we derive approximate formulas for amplitudes and polarizations of waves reflected from and transmitted through a planar, horizontal boundary between an overlying isotropic medium and an underlying tilted transversely isotropic (TTI) medium assuming that the directions of the phase and group velocities are consistent. Provided that the velocities in the isotropic medium are equal to the velocities along the symmetry axis direction, we derive the relational expression between the propagation angle in the TTI medium and the propagation angle in the hypothetical isotropic medium, under the condition that the horizontal slowness is the same, and then we update the approximate formula of the polarization in the TTI medium. Provided that the slow and fast transverse waves (qS and SH) are generated simultaneously in the anisotropic interface, we linearize for a six-order Zoeppritz equation, derive the azimuthal formula of longitudinal and S-waves, and determine their detailed expressions within the symmetry axis plane. According to the derived azimuthal AVO formula, we establish medium models, compare the derived AVO with the precision, and obtain the following conclusions: (1) The dip angle for the symmetry axis with respect to the vertical may have a sufficiently large impact on AVO, and the vertical longitudinal wave can generate an S-wave. (2) For the derived AVO formula, within the symmetry axis plane, the fitting effect of the approximate and exact formulas is good; however, within the other incident planes, taking the azimuth angle 45° as an example, the approximation is suitable for the large impedance contrast if the anisotropic parameters are set properly. (3) The error between the approximation and precision is mainly caused by the difference between the reflected and transmitted angles, the velocities’ derivation with respect to azimuth, and the division of approximation into isotropic and anisotropic parts.

On the determination of the polarization angle of the S wave

1962 ◽  
Vol 52 (1) ◽  
pp. 95-107
Author(s):  
Otto Nuttli ◽  
John D. Whitmore
Keyword(s):  
Wave Velocity ◽  
Particle Motion ◽  
Poisson’S Ratio ◽  
Epicentral Distance ◽  
Critical Distance ◽  
P Wave ◽  
Poisson's Ratio ◽  
Polarization Angle ◽  
Angle Of Incidence ◽  
S Wave

Abstract This study is concerned with determining the minimum epicentral distance for which it is permissible to obtain the value of the polarization angle of the S wave by measuring the angle between the great circle path at the station and the direction of the horizontal component of the S wave particle motion obtained from the seismograms. This critical distance can be determined by the fact that at smaller distances the particle motion of the earth's surface due to the incidence of S will be nonlinear (the SH and the horizontal and vertical components of SV will be out of phase with respect to one another) while at larger distances the particle motion will be linear. An analysis of the S motion recorded by the Galitzin-Wilip seismographs at Florissant indicates that the critical distance is 42 degrees. The periods of these S waves are of the order of 10 second. The analysis also shows that the effective P wave velocity of teleseismic waves at the earth's free surface is 7.74 km/sec, and the effective value of Poisson's ratio and the effective S wave velocity at the earth's surface are 0.25 and 4.46 km/sec, respectively. By effective values are meant the values of the velocities and Poisson's ratio that govern the angle of incidence of the waves at the earth's surface.

Strong-Motion Accelerograms of the Oroville, California, aftershocks: Data processing and the aftershock of 0350 August 6, 1975

1980 ◽  
Vol 70 (1) ◽  
pp. 243-267
Author(s):  
Jon B. Fletcher ◽  
A. Gerald Brady ◽  
Thomas C. Hanks
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Seismic Moment ◽  
Strong Motion ◽  
P Wave ◽  
S Wave ◽  
Quality Of Data ◽  
Pass Filter ◽  
Processing Scheme ◽  
Field Source

abstract The Oroville aftershock accelerograms are characterized by short durations (≲2 sec) of strong ground motion, small S-wave minus trigger times (≲2 sec), and an enrichment in frequencies above 1 Hz, as might be expected for 3 ≲ M ≲5 earthquakes recorded at close distances (R ≲ 15 km). These characteristics introduce significant error into the velocity and displacement traces calculated according to the routine procedures used in the series “Strong Motion Earthquake Accelerograms.” These errors are markedly reduced by removing all decimation in the processing scheme and by constructing a smoother response for the Ormsby high-pass filter. The result is an accurate set of velocity and displacement traces that can be used in a wide variety of source-mechanism and ground-motion studies. These revised processing procedures are applied to the ten strong-motion accelerograms of one of the largest aftershocks (0350 August 6, 1975; ML = 4.7) to illustrate the quality of data available for 12 such well-recorded aftershocks and to estimate the source properties of this particular earthquake. All of the accelerographs triggered on the P wave, allowing the recovery of the complete S wave on ten accelerograms. Offsets in displacement across the S wave and a ramp-like signature leading up to the S wave identified on the displacement traces are apparently near-field source effects. The seismic moment and stress drop determined for this normal faulting event are 4.0 × 1023 dyne-cm, and 410 bars, respectively. The seismic moment and stress drop are determined by averaging individual measurements at 9 and 8 stations, respectively, and are well-constrained with standard deviations that are about 25 per cent of the mean.

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 

scholarly journals Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Philipp Balling ◽  
Christoph Grützner ◽  
Bruno Tomljenović ◽  
Wim Spakman ◽  
Kamil Ustaszewski
Keyword(s):  
Balkan Peninsula ◽  
Receiver Functions ◽  
P Wave ◽  
S Wave ◽  
Slab Geometry ◽  
Surface Uplift ◽  
River Incision ◽  
Marine Terraces ◽  
Convergence System ◽  
Internal Dinarides

AbstractThe Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

scholarly journals S-wave experiments for the exploration of a deep geothermal carbonate reservoir in the German Molasse Basin

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Britta Wawerzinek ◽  
Hermann Buness ◽  
Hartwig von Hartmann ◽  
David C. Tanner
Keyword(s):  
Upper Jurassic ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Molasse Basin ◽  
S Wave ◽  
Induced Earthquakes ◽  
Conversion Point ◽  
Facies Classification

AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.

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