Spectral source parameters for weak local earthquakes in the Pannonian basin

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Bálint Süle
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Pannonian Basin ◽  
Source Parameters ◽  
Active Regions ◽  
P Wave ◽  
Local Earthquakes ◽  
Scaling Relationship ◽  
Dynamic Source ◽  
Relationship Of

AbstractDynamic source parameters are estimated from P-wave displacement spectra for 18 local earthquakes (1.2 < ML < 3.7) that occurred in two seismically active regions of Hungary between 1995 and 2004. Although the geological setting of the two areas is quite different, their source parameters cannot be distinguished. The source dimensions range from 200 to 900 m, the seismic moment from 6.3x1011 to 3.48×1014 Nm, the stress drop from 0.13 to 6.86 bar, and the average displacement is less than 1 cm for all events. The scaling relationship between seismic moment and stress drop indicates a decrease in stress drop with decreasing seismic moment. A linear relationship of M w = 0.71 M L + 0.92 is obtained between local magnitude and moment magnitude.

Estimation of Source Parameters and their scaling relationship of small to moderate magnitude earthquakes for northeast India

2021 ◽  
Author(s):  
Prosanta Kumar Khan ◽  
Bandana Baruah
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Body Wave ◽  
Source Parameters ◽  
Empirical Relationship ◽  
Northeast India ◽  
Corner Frequency ◽  
Scaling Relationship ◽  
Brahmaputra Basin ◽  
Relationship Of

&lt;p&gt;We investigate the source parameters of 87 local earthquakes (3.5 &amp;#8804; M&lt;sub&gt;L&lt;/sub&gt; &amp;#8804; 5.0) that occurred in West Brahmaputra basin and its neighbouring area, using body wave displacement spectra. Seismic moment, corner frequency, source dimension and static stress drop are estimated using a grid search method based on the model of circular source. The measured seismic moments, corner frequency and moment magnitude ranges from &amp;#160; to &amp;#160;N-m, 0.7 to 12.1 and 3.0 to 4.8, respectively. The average ratio of corner frequency of P - and S - waves is 2.21.&lt;strong&gt; &lt;/strong&gt;The scaling relationship of seismic moment against corner frequency is also studied for various tectonics regimes separately. Median stress drop values of individual earthquake vary from ~ 0.1 to 38.5 MPa, with an average value of about ~ 6 MPa. Spatial variation of stress drop observed for different tectonic unit reveals a higher stress drop values associated with West Brahmaputra basin, Shillong-Mikir plateau and Indo-Myanmar subduction zone suggesting a higher stress accumulation that may increase the probability of higher magnitude earthquake. The empirical relationship between M&lt;sub&gt;L&lt;/sub&gt; and M&lt;sub&gt;W&lt;/sub&gt; scale is also derived for hazard assessment.&lt;/p&gt;

scholarly journals Seismic Moment, Stress Drop, Strain Energy, Dislocation Radius, and Location of Seismic Acoustic Emissions Associated with a High Alpine Snowpack at Berthoud Pass, Colorado, U.S.A. (Abstract only)

1983 ◽  
Vol 4 ◽  
pp. 304-304
Author(s):  
Charles Cleland Rosé
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Source Parameters ◽  
Acoustic Emissions ◽  
Body Waves ◽  
P Wave ◽  
Dissipated Energy ◽  
Fracture Area ◽  
Stress Drops ◽  
Predictive Indicator

The monitoring of the number of acoustic seismic impulses arising from snow instabilities is regarded as a relative indicator of an unstable snow slope but has not yielded a qualitative, predictive indicator. Until now, the source parameters (fracture area and length), seismic moment, energy released, stress drop, and location of acoustic seismic emissions arising from the snowpack have been neglected. A comprehension of these parameters leads to a better understanding of the event and may help in avalanche prediction.The location of a seismic event is derived from time differences between P-wave arrivals at four sensors located at the snow-ground interface. Three methods confirm the location of an acoustic seismic snow event to within 2 to 4 cm when the event is inside a seismic net.Spectral analyses of body waves from seismic snow events yield estimates of source parameters, stress drop and energy released. Equivalent dislocation surface radii range from 4.8 to 9.0 cm, which give stress drops of 0.20 to 0.29 bar, with a dissipated energy in the range of 0.0205 to 0.0632 J.Spectral analysis of the acoustic seismic snow event with application of dislocation theory provides several likely methods to predict avalanches of a climax type.

scholarly journals Seismic Moment, Stress Drop, Strain Energy, Dislocation Radius, and Location of Seismic Acoustic Emissions Associated with a High Alpine Snowpack at Berthoud Pass, Colorado, U.S.A. (Abstract only)

1983 ◽  
Vol 4 ◽  
pp. 304
Author(s):  
Charles Cleland Rosé
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Source Parameters ◽  
Acoustic Emissions ◽  
Body Waves ◽  
P Wave ◽  
Dissipated Energy ◽  
Fracture Area ◽  
Stress Drops ◽  
Predictive Indicator

The monitoring of the number of acoustic seismic impulses arising from snow instabilities is regarded as a relative indicator of an unstable snow slope but has not yielded a qualitative, predictive indicator. Until now, the source parameters (fracture area and length), seismic moment, energy released, stress drop, and location of acoustic seismic emissions arising from the snowpack have been neglected. A comprehension of these parameters leads to a better understanding of the event and may help in avalanche prediction. The location of a seismic event is derived from time differences between P-wave arrivals at four sensors located at the snow-ground interface. Three methods confirm the location of an acoustic seismic snow event to within 2 to 4 cm when the event is inside a seismic net. Spectral analyses of body waves from seismic snow events yield estimates of source parameters, stress drop and energy released. Equivalent dislocation surface radii range from 4.8 to 9.0 cm, which give stress drops of 0.20 to 0.29 bar, with a dissipated energy in the range of 0.0205 to 0.0632 J. Spectral analysis of the acoustic seismic snow event with application of dislocation theory provides several likely methods to predict avalanches of a climax type.

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.

scholarly journals Earthquake Seismic Moment, Rupture Radius and Stress-drop from P-wave Displacement Amplitude vs Time Curves

2021 ◽  
Author(s):  
aldo zollo ◽  
sahar nazeri ◽  
Simona Colombelli
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Central Italy ◽  
Average Stress ◽  
Displacement Amplitude ◽  
P Wave ◽  
Parametric Modelling ◽  
Peak Displacement ◽  
Reliable Determination ◽  
Anelastic Attenuation

The reliable determination of earthquake source parameters is a relevant task of seismological investigations which ground nowadays on high quality seismic waveforms collected by near-source dense arrays of ground motion sensors. Here we propose a parametric modelling technique which analyzes the time-domain P-wave signal recorded in the near-source range of small-to-large size earthquakes. Assuming a triangular moment-rate function and a uniform speed, circular rupture model, we develop the equations to estimate the seismic moment, rupture radius and stress-drop from the corner-time and plateau level of the average logarithm of the P-wave displacement vs time curves (LPDT). The constant-Q, anelastic attenuation effect is accounted by a post-processing procedure that evaluates the Q-unperturbed moment-rate triangular shape.<br>The methodology has been validated through the application to the acceleration records of the 2016-2017 Central Italy and 2007-2019 Japan earthquake sequences covering a wide moment magnitude range (Mw 2.5 - 6.5) and recording distance < 100 km. After correcting for the anelastic attenuation function, the estimated average stress-drop and the confidence interval (〈∆σ〉=0.60 (0.42-0.87) MPa and 〈∆σ〉=1.53 (1.01-2.31) for crustal and subcrustal events of Japan and 〈∆σ〉=0.36(0.30-0.44) MPa for Central Italy) show, for both regions, a self-similar, constant stress-drop scaling of the rupture duration/radius with seismic moment. The smaller sensitivity of the spatially averaged, time-varying peak displacement amplitude to the radiation from localized high slip patch on the fracture surface, could explain the retrieved smaller average stress-drops for sub-crustal earthquakes in Japan and M>5.5 events in Central Italy relative to previous estimates using spectral methods.<br><br>

scholarly journals ANALISIS PARAMETER SUMBER SPEKTRAL GEMPABUMI VTA (VULKANO TEKTONIK-A) TERHADAP AKTIVITAS VULKANIK GUNUNG SINABUNG

2019 ◽  
Vol 5 (1) ◽  
pp. 18-23
Author(s):  
Tri Kusmita ◽  
Kirbani Brotopuspito ◽  
Hetty Triastuty
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Source Parameters ◽  
Radiation Energy ◽  
Angular Frequency ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Volcanic Earthquake ◽  
Seismic Volumes ◽  
The Relationship

The source parameters describe the different physical properties of seismic volumes under the volcanoes. Source parameters that can be used to distinguish seismic events that are generated by different types of volcanoes activities. Temporary changes of the spectral source parameters provided a description of the main events during the eruption process.  Source parameters are calculated by correlating the relationship between source frequency at spectral displacement (corner frequency) and source parameters based on spectral sources of the Brune model (1970). The angular frequency obtained by applying the FFT algorithm to the VTA spectral displacement. The source parameters analyzed from this VTA earthquake are the spectral slope, seismic moment, stress drop, length of rupture, moment magnitude and radiation energy. Based on the obtained corner frequency (12 Hz-13 Hz), seismic moment, moment magnitude and energy radiation respectively were at 0.2 -1.9 x 1012 Nm, 0.7 - 2 Mw, and 0.1 - 9.5 x 1015 erg. The length of rupture were from 144.2 to 243.1 m, the spectra slope has 2.1 - 7.8 dB/cm, and stress drop are 0.1 - 7,6 bar. From the results of this study, it can be concluded that the changes of spectra characteristic and fluctuate of source patrameters value of VTA earthquakes was asosiated with the different  volcanic activity of Sinabung. Keywords: spectral, VTA, source parameter, volcanic earthquake

Simultaneous inversion for Q and source parameters of microearthquakes accompanying hydraulic fracturing in granitic rock

1991 ◽  
Vol 81 (2) ◽  
pp. 553-575 ◽  
Author(s):  
Michael Fehler ◽  
W. Scott Phillips
Keyword(s):  
Hydraulic Fracturing ◽  
Stress Drop ◽  
Source Parameters ◽  
Low Frequency ◽  
Seismic Energy ◽  
P Wave ◽  
Corner Frequency ◽  
Spectral Amplitude ◽  
Seismic Zone ◽  
Stress Drops

Abstract An inversion that fits spectra of earthquake waveforms and gives robust estimates of corner frequency and low-frequency spectral amplitude has been used to determine source parameters of 223 microearthquakes induced by hydraulic fracturing in granodiorite. Assuming a ω−2 source model, the inversion fits the P-wave spectra of microearthquake waveforms to determine individual values of corner frequency and low-frequency spectral amplitude for each event and one average frequency-independent Q for all source-receiver paths. We also implemented a constraint that stress drops of all microearthquakes be similar but not equal and found that this constraint did not significantly degrade the quality of the fits to the spectra. The waveforms analyzed were recorded by a borehole seismometer. The P-wave Q was found to be 1070. For Q values as low as 600 and as high as 3000, the misfit between model and spectra increased by less than 5 per cent and the average corner frequency changed by less than 15 per cent from those obtained with a Q of 1070. Average stress drop was 3.7 bars. Seismic moments obtained from spectra ranged from 1013 to 1018 dyne-cm. The low stress drops are interpreted to result from underestimation of the actual stress drops because of a nonuniform distribution of stress drop and slip along the fault planes. Spatially varying stress drops and slips result from the strong rock heterogeneity due to the injection of fluid into the rock. Stress drops were found to be larger near the edges of the seismic zone, in regions that had not been seismically active during previous injections. The seismic moments determined from spectra were used to obtain a coda length-to-moment relation. Then, moments were estimated for 1149 events from measurements of coda lengths from events whose moments could not be measured from spectra because of saturation or a low signal-to-noise ratio. The constant of proportionality between cumulative number of events and seismic moment is higher than that found for tectonic regions. The slope is so high that the seismic energy release is dominated by the large number of small events. In the absence of information about the number of events smaller than we studied, we cannot estimate the total seismic energy released by the hydraulic injection.

Far-field pulse shapes from circular sources with variable rupture velocities

1997 ◽  
Vol 87 (5) ◽  
pp. 1288-1296
Author(s):  
Nicholas Deichmann
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Total Duration ◽  
Source Model ◽  
P Wave ◽  
Far Field ◽  
Rupture Velocity ◽  
P Waves ◽  
S Waves ◽  
Rate Functions

Abstract Recently, Sato (1994) developed a simple earthquake source model of a circular rupture expanding outward from the center of a fault with constant stress drop. In contrast to previous models, the rupture velocity is allowed to vary over the duration of faulting. This model is used to synthesize apparent moment-rate functions for a three-stage source process: first, the rupture starts out with a gradually increasing velocity, then, it continues to expand uniformly until, finally, it slows to a gradual stop. Synthetic velocity seismograms are obtained from a convolution of the apparent moment-rate functions with a causal Q-operator and an appropriate instrument response. Comparisons with an example of an earthquake signal show that, in the context of the proposed model, the observed emergent P-wave onset, which is not compatible with a constant rupture velocity, can be explained by a gradually accelerating rupture front. Systematic departures from the generally expected scaling relationship between seismic moment and rupture duration are often interpreted as evidence for a dependence of stress drop on seismic moment. However, the trade-off between stress drop and rupture velocity inherent in all kinematic source models implies that such deviations can just as well be attributed to systematic variations of rupture velocity. Whereas, in general, the total duration of the far-field displacement pulse is shorter for P waves than for S waves, the model predicts that the rise time, τ1/2, of the displacement pulse should be longer for P waves than for S waves. This feature could constitute a critical test of the model and also provide a constraint on the rupture velocity.

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