Stress Drop, Apparent Stress, and Radiation Efficiency of Clustered Earthquakes in the Nucleation Volume of the 6 April 2009, M w 6.1 L'Aquila Earthquake

2019 ◽  
Vol 124 (10) ◽  
pp. 10360-10375
Author(s):  
Giovanna Calderoni ◽  
Antonio Rovelli ◽  
Rita Di Giovambattista
Keyword(s):  
Stress Drop ◽  
Radiation Efficiency ◽  
Apparent Stress ◽  
L’Aquila Earthquake

Spatio-temporal variations of source parameters in the nucleation zone of the 6 April 2009, Mw 6.1 L'Aquila Earthquake

2020 ◽  
Author(s):  
Rita Di Giovambattista ◽  
Giovanna Calderoni ◽  
Antonio Rovelli
Keyword(s):  
Stress Drop ◽  
Main Shock ◽  
Source Parameters ◽  
Dynamic Strength ◽  
Temporal Variations ◽  
Apparent Stress ◽  
L’Aquila Earthquake ◽  
Focal Volume ◽  
Spatio Temporal ◽  
The Individual

<p>We present the results of Brune stress drop (∆σ) and apparent stress (τa) variability of  earthquakes located in a small zone adjacent to the hypocenter of the damaging Mw 6.1 L'Aquila earthquake. Their magnitude ranges between  2.7 and 4.1. Interevent variability of stress drop and apparent stress results in a factor of 10, well beyond the individual‐event uncertainty. Radiation efficiency ηsw = τa/∆σ varies mostly between 0.1 and 0.2, but decreases in the days immediately before and after the main shock to values as low as 0.06. This may be related to the migration of the events occurring in those days into a focal volume with higher dynamic strength. The temporal change of ηsw might be interpreted as a spatial variation due to the earthquake migration into the locked portion of the fault originating the main shock. Furthermore, no variation in stress drop and apparent stress can be observed between foreshocks and aftershocks but the smallest and largest ∆σ result in a good correlation with the largest and smallest b‐values respectively, as already documented in literature in the rupture nucleation volume of large earthquakes.</p>

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.

Stress drop estimates for some aftershocks of the Ometepec, Guerrero, Mexico, earthquake of June 7, 1982

1987 ◽  
Vol 24 (8) ◽  
pp. 1727-1733 ◽  
Author(s):  
Cecilio J. Rebollar ◽  
Rosa M. Alvarez
Keyword(s):  
Stress Drop ◽  
Wave Attenuation ◽  
Seismic Energy ◽  
Coda Wave ◽  
Apparent Stress ◽  
Radiated Seismic Energy ◽  
Seismic Coda ◽  
Seismic Quality Factor ◽  
Single Station ◽  
Stress Drops

Brune's stress drop, apparent stress, and arms stress drop are estimated at a single station for 25 aftershocks of the Ometepec earthquakes (Ms = 6.9 and Ms = 7.0). The arms stress drops and apparent stresses are systematically smaller than Brune's stress drops. Stress drops from the root mean square of acceleration and apparent stress range from 0.01 to 10.2 bars (1 bar = 100 kPa) except for two values (21.4 and 33.0 bars). On the other hand, Brune's stress drops range from 0.6 to 239 bars. Seismic moments ranging from 0.5 × 1019 to 289 × 1019 dyn∙cm (1 dyn∙cm = 10 μN∙cm) were estimated for events with coda magnitudes between 0.6 and 2.2. Values of radiated seismic energy calculated by integration of the displacement spectra range from 2.5 × 1012 to 2.3 × 1016 dyn∙cm. The fmax values lie between 16 and 30 Hz. Seismic coda wave attenuation measured on narrow band-pass-filtered seismograms show a linear dependence of the seismic quality factor of the form [Formula: see text] in the range of frequencies from 3 to 24 Hz.

Apparent stress and stress drop for intraplate earthquakes and tectonic stress in the plates

1977 ◽  
Vol 115 (1-2) ◽  
pp. 317-331 ◽  
Author(s):  
Randall M. Richardson ◽  
Sean C. Solomon
Keyword(s):  
Stress Drop ◽  
Tectonic Stress ◽  
Apparent Stress ◽  
Intraplate Earthquakes

scholarly journals Variability in earthquake stress drop and apparent stress

2011 ◽  
Vol 38 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Annemarie Baltay ◽  
Satoshi Ide ◽  
German Prieto ◽  
Gregory Beroza
Keyword(s):  
Stress Drop ◽  
Apparent Stress

scholarly journals DOUBLET of DOMBAI EARTHQUAKES 2013 in FOCAL ZONE of CHKHALTA EARTHQUAKE 1963

2019 ◽  
pp. 362-369 ◽  
Author(s):  
Irina Gabsatarova ◽  
L. Koroletski ◽  
L. Malyanova
Keyword(s):  
Stress Drop ◽  
Strike Slip ◽  
Geodynamic Setting ◽  
Reverse Fault ◽  
Apparent Stress ◽  
S Waves ◽  
Greater Caucasus ◽  
Rupture Length ◽  
Focal Zone ◽  
Good Agreement

Two Dombai earthquakes were recorded on March 26, 2013, at 23h35m with КР=11.9 and on May 28, 2013, at 00h09m with КР=11.9 (Mw GCMT=4.9 and 5.2) in the focal area of two strong (I0=IX and I0=VII at MSK 64) Chkhalta of 1963 and Teberda of 1905 earthquakes. They were accompanied by aftershock pro-cesses. The estimates of dynamic parameters of foci (for March 26, 2013, then May 28, 2013): the rupture length is L=3.4, 3.8 km, the stress drop =55, 79 Pa, the apparent stress drop=1, 3 Pa, and the average displacement along the rupture u=0.25, 0.33 m, were obtained from the spectra of S-waves at “Anapa” and “Kislovodsk” stations. Earthquakes occurred under the action of near-horizontal (PL=12°, PL=18°) com-pressive stresses directed north-northeast (AZM=21°, AZM=30°). The nodal planes of both mechanisms have a similar strike. The type of movement in both foci is a reverse fault with some strike-slip components. The stretches of nodal planes and the types of movements in the foci are in good agreement with the geodynamic setting of the axial structures of the Greater Caucasus, and also are similar to the mechanism of the destructive Chkhalta earthquake of 1963.

Far-field radiated energy scaling in elastodynamic earthquake fault models

1998 ◽  
Vol 88 (6) ◽  
pp. 1457-1465
Author(s):  
Bruce E. Shaw
Keyword(s):  
Stress Drop ◽  
Field Energy ◽  
Far Field ◽  
Apparent Stress ◽  
Fault Models ◽  
Conservation Of Energy ◽  
Rupture Length ◽  
Radiated Energy ◽  
Sequence Of Events ◽  
Wide Range

Abstract Measurements of the far-field radiated energy in very simple elastodynamic fault models is presented, and the scaling of the radiated energy with moment and rupture length is examined. The models produce a complex sequence of events having a wide range of sizes as a result of a frictional-weakening instability. Thus, radiated energy from a broad range of sizes of events can be measured. Using conservation of energy, I am able to measure the far-field energy very accurately and efficiently. I study a range of frictions, from velocity weakening to slip weakening, in order to examine the effects of the physics of the rupture source on the radiated energy. Examining the scaling of radiated energy as a function of moment and rupture length, I find differences for slip-weakening as compared to velocity-weakening friction. I find distinct differences in how the apparent stress scales with moment and also how the apparent stress divided by the stress drop scales with moment for the different frictions. Most dramatically, the apparent stress divided by the stress drop is significantly smaller for slip weakening relative to velocity weakening. This suggests that measurements of radiated energy versus moment and rupture length in earthquakes, combined with forward elastodynamic modeling, can be used to constrain possible source physics.

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