Coda Q before the 1983 Hawaii (MS = 6.6) earthquake

1988 ◽  
Vol 78 (3) ◽  
pp. 1279-1296
Author(s):  
Zhong-Xian Huang ◽  
Max Wyss
Keyword(s):  
Unit Volume ◽  
Main Shock ◽  
B Value ◽  
Rectangular Region ◽  
S Wave ◽  
Coda Q ◽  
Seismicity Rate ◽  
High Q ◽  
Source Mechanisms ◽  
Q Values

Abstract Coda Q values were derived for more than 300 microearthquakes that occurred in a 6-yr period before the 16 November 1983 Kaoiki, Hawaii, earthquake (MS = 6.6). The sources were located within a 14 × 16 km rectangular region surrounding the main shock epicenter, and most of them occurred at depths between 5 and 10 km. Digital recordings from three stations at epicentral distances ranging from 0 to 18 km were used. Coda Q was calculated from the amplitude decay rate of the S-wave coda in nine frequency bands from 4.5 to 27 Hz. The average Q of the NW part of the studied area is about 15 per cent higher than that of the SE part. These two subregions also showed differences in seismicity, b value, and microearthquake source mechanisms. In the high-Q volume, the b value was 1.0, and the rate of earthquakes per unit volume was about 50 per cent of the rate in the low-Q volume where b = 1.3. One interpretation of these observations is that more extensive faulting in the SE Kaoiki fault zone leads to lower Q, higher b value, and a higher seismicity rate. During the 5 to 6 yr before the mainshock, the 1-yr average Q values were stable. No significant Q change could be identified as a precursor to the main shock.

S-wave attenuation in the crust in northern Greece

1995 ◽  
Vol 85 (5) ◽  
pp. 1381-1387 ◽  
Author(s):  
P. M. Hatzidimitriou
Keyword(s):  
Wave Attenuation ◽  
Amplitude Ratio ◽  
Single Scattering ◽  
Coda Wave ◽  
S Wave ◽  
Coda Q ◽  
Northern Greece ◽  
Single Station ◽  
The University ◽  
Q Values

Abstract The attenuation of shear waves in the crust is estimated, for frequencies between 1.5 and 12.0 Hz, by applying a single-station method based on the rate of decay of the S-wave to coda-wave amplitude ratio with distance. The data used come from local earthquakes that occurred in the Thessaloniki area, northern Greece, during the period 1983 through 1989 and were recorded by the telemetered network of the Geophysical Laboratory of the University of Thessaloniki. The Qs values obtained are 115, 244, 477, and 755 for 1.5, 3.0, 6.0, and 12.0 Hz, respectively. These values are very close to the coda Q values estimated for the same area using the S-to-S single scattering model for lapse times between 30 and 100 sec but they are higher than the coda Q values for lapse times between 10 and 30 sec. The estimated Qs is found to be strongly frequency dependent, proportional to f0.91, which is very close to the frequency dependence of the coda Q.

Volcano-tectonic earthquake statistics for Campi Flegrei monitoring

2020 ◽  
Author(s):  
Anna Tramelli ◽  
Cataldo Godano ◽  
Flora Giudicepietro ◽  
Patrizia Ricciolino ◽  
Stefano Caliro
Keyword(s):  
Risk Mitigation ◽  
Central Area ◽  
B Value ◽  
Campi Flegrei ◽  
Occurrence Rate ◽  
Value Change ◽  
Tectonic Earthquake ◽  
Seismicity Rate ◽  
Seismic Catalogue ◽  
Source Mechanisms

<p><span>The knowledge of the dynamic of the Campi Flegrei calderic system is </span><span>essential</span><span> to mitigate the volcanic risk in one of the most densely populated volcanic areas in the world. From 1950 to 1985 three bradyseismic crises </span><span>occurred</span><span> with a total uplift of </span><span>almost 3 m (Del Gaudio et al., 2010). After more than 20 years of subsidence, at the end of 2005 the uplift started again accompanied by a low increment in the seismicity rate. In 2012 a further increment in the seismicity rate was observed and a variation in the gas composition of the fumaroles of Solfatara (central area of the caldera) revealed the injection of magmatic fluids into the hydrothermal system (Chiodini et al., 2017). This suggests that the investigation of the seismicity can represent a very useful tool for the risk mitigation. Here we analyze the seismic catalogue of Campi Flegrei (collected by INGV - Osservatorio Vesuviano) to check for any variation of the observed seismicity. This can be eventually associated with geochemical monitored parameters. </span><span>In addition, we analyzed the most energetic swarms recorded in this period by comparing their locations, waveforms and source mechanisms.</span><span> We find that occurrence rate, location and b-value change in time. The seismicity occurs in swarms, which</span><span>, in the last years, tends to became closer but with a smaller number of events.</span><span> The </span><span>observed </span><span>variations are correlated also with </span><span>the</span><span> geochemical monitoring parameters suggesting that the uplift process has probably modified the elastic and permeability properties of the shallow part of the crust. </span></p>

Measurements of intrinsic and scattering seismic attenuation in the crust

1995 ◽  
Vol 85 (5) ◽  
pp. 1373-1380 ◽  
Author(s):  
Edoardo Del Pezzo ◽  
Jesus Ibanez ◽  
José Morales ◽  
Aybige Akinci ◽  
Rosalba Maresca
Keyword(s):  
Seismic Attenuation ◽  
Campi Flegrei ◽  
Etna Volcano ◽  
S Wave ◽  
Coda Q ◽  
Shallow Earthquakes ◽  
Tectonically Active ◽  
Intrinsic And Scattering Attenuation ◽  
Q Values ◽  
Degree Of Heterogeneity

Abstract Intrinsic and scattering attenuation parameters, Qi and QS, have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver. The approach developed by Wennerberg (1993), which takes into account the numerical correction of the coda-Q parameter for the multiple scattering formulation of Zeng, was used to infer from the estimates of coda Q and direct S-wave Q the intrinsic (Qi) and scattering (QS) Q values. Results for 1 to 12 Hz range show that Qi is comparable to QS for the Etna volcano and for the Campi Flegrei area, while Qi for the tectonically active area of Granada is lower than QS. Coda Q is close to intrinsic Q, suggesting that, at least in the crust, coda Q is a good estimate of the intrinsic Q. Volcanic areas show a reasonable higher degree of heterogeneity, if compared with the nonvolcanic area of Granada.

Source dynamics of two great earthquakes of the Indian subcontinent: The Bihar-Nepal earthquake of January 15, 1934 and the Quetta earthquake of May 30, 1935

1980 ◽  
Vol 70 (3) ◽  
pp. 757-773
Author(s):  
D. D. Singh ◽  
Harsh K. Gupta
Keyword(s):  
Main Shock ◽  
Indian Subcontinent ◽  
High Stress ◽  
P Wave ◽  
Wave Polarization ◽  
S Wave ◽  
Temporal And Spatial Variation ◽  
Regional Seismicity ◽  
Source Mechanisms ◽  
Temporal And Spatial

abstract Source mechanisms of two major destructive earthquakes which occurred at the Bihar-Nepal border and in the Quetta region on January 15, 1934 and May 30, 1935, respectively, are determined using the P-wave first motions, S-wave polarization angles, and surface-wave spectral data. The high stress drop and apparent stress associated with these events suggest that high tectonic stresses are prevailing in these regions. A major part of the stresses accumulated before the occurrence of the two earthquakes had been released through the main shock. An investigation of temporal and spatial variation of regional seismicity reveals possible existence of seismic gaps before the occurrence of these two major events.

scholarly journals Earthquake clusters in NW Peloponnese.

2016 ◽  
Vol 47 (3) ◽  
pp. 1167
Author(s):  
M. Mesimeri ◽  
E. Papadimitriou ◽  
V. Karakostas ◽  
G. Tsaklidis
Keyword(s):  
Spatial Distribution ◽  
Main Shock ◽  
B Value ◽  
Earthquake Swarms ◽  
Background Rate ◽  
Seismicity Rate ◽  
Seismic Moment Release ◽  
Earthquake Clusters ◽  
Stress Accumulation ◽  
Skewness And Kurtosis

Clusters commonly occur as main shock – aftershock (MS-AS) sequences but also as earthquake swarms, which are empirically defined as an increase in seismicity rate above the background rate without a clear main shock. A delcustering algorithm is employed to identify clusters from a complete catalog of earthquakes that occurred in the area of NW Peloponnese (Greece) during 1980-2007. In order to distinguish these clusters we calculate the skewness and kurtosis of seismic moment release for each cluster, since swarm-like sequences generally have lower skew value of moment release history than MS-AS. The spatial distribution of b-value was calculated for the entire catalog as for the declustered one, in order to correlate them with seismicity behavior of the region. Finally, the pre-stress field of Achaia 2008 earthquake was calculated aiming to associate the stress accumulation with the occurrence of the identified clusters

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

Microearthquake activity following the Parkfield, California earthquake of June, 1966

1969 ◽  
Vol 59 (2) ◽  
pp. 603-613
Author(s):  
Thomas J. Fitch
Keyword(s):  
Main Shock ◽  
High Sensitivity ◽  
Amplitude Distribution ◽  
B Value ◽  
Epicentral Area ◽  
San Andreas ◽  
Recording Station ◽  
Parkfield Earthquake ◽  
Secondary Aftershock ◽  
Secondary Fault

abstract A high sensitivity microearthquake recording station was established 10 km from the epicenter of the magnitude 5.5 Parkfield earthquake of June 28, 1966. Beginning 43 hours after the main shock, an hourly average of 22 microaftershocks was recorded for a period of 13 days. Events with magnitudes roughly equivalent to a Richter magnitude of −1.5 were recorded. The amplitude distribution suggests that there was a smaller percentage of small shocks in the Parkfield microaftershock series than has commonly been reported for Japanese and other California aftershock series. b values between 0.8 and 0.9 are commonly reported while the average b value for the Parkfield microaftershock series was 0.59. The distribution of S-P times for the microaftershocks is consistent with the epicentral area defined in other studies as a strip approximately 5 km wide astride a 35 km long trace of the San Andreas fault; however, some evidence suggests that the microaftershock activity extends beyond the zone defined by the larger aftershocks. The spatial distribution of microearthquake activity is shown to be strongly non-uniform within the aftershock zone. The microaftershocks, in general, did not cluster in time about the larger aftershocks (M > 2.0). Of 24 aftershocks with M greater than or equal to 2.0, only one event gave strong evidence of triggering a secondary aftershock series. Assuming that secondary foreshock and/or aftershock series imply the creation or reactivation of a secondary fault, one is led to the conclusion that secondary faulting was a rare occurrence in the Parkfield aftershock zone.

Nowcasting and multifractal features of the seismicity in the subduction zone of Tehuantepec Isthmus, southern México

2021 ◽  
Author(s):  
Alejandro Ramírez-Rojas ◽  
Elsa Leticia Flores-Márquez
Keyword(s):  
Main Shock ◽  
B Value ◽  
Fluctuation Analysis ◽  
Southern Mexico ◽  
Multifractal Detrended Fluctuation Analysis ◽  
Middle America Trench ◽  
Seismicity Distribution ◽  
Isthmus Of Tehuantepec ◽  
Temporal Rate ◽  
Detrended Fluctuation

<p>After the M8.2 earthquake occurred on September 07, 2017 at Isthmus of Tehuantepec, notable spatial and temporal changes where<br>registered, the temporal rate of occurrence increased and the spatial seismicity distribution showed a clear clusterization along<br>the region of collision of the Tehuantepec Transform/Ridge with the Middle America Trench off Chiapas. Also, the b-value in the<br>Gutenberg-Richer law showed changes in time. On the basis of that behavior we studied the sequence of magnitudes of the<br>earthquakes occurred within the Isthmus of Tehuantepec at southern Mexico from 2010 to 2020, by using the nowcasting method<br>and the multifractal detrended fluctuation analysis. Our findings suggest the b-value could depend on time and after the main-shock<br>M8.2, the underlying dynamics in the Tehuantepec ridge has been changed, which is clearly described by our analyses based on<br>nowcasting method and in the multifractality estimated changes.</p>

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