Focal depths and source parameters of the Rocky Mountain House earthquake swarm from digital data at Edmonton

1984 ◽  
Vol 21 (10) ◽  
pp. 1105-1113 ◽  
Author(s):  
C. J. Rebollar ◽  
E. R. Kanasewich ◽  
E. Nyland
Keyword(s):  
Epicentral Distance ◽  
Source Parameters ◽  
Earthquake Swarm ◽  
Focal Depth ◽  
Rocky Mountain ◽  
Small Variation ◽  
B Value ◽  
Digital Data ◽  
The Difference ◽  
Stress Drops

Seismic records at Edmonton (EDM) and Suffield (SES) between January 1976 and February 1980 show 220 events with magnitudes less than 4 originating near Rocky Mountain House. Many of these events show well defined Sn, Sg, and Pg phases and a small variation in the difference of Sg − Sn and Sg − Pg. Analysis of the theoretical travel times using a structure determined for central Alberta yields an average focal depth of 20 ± 5 km and an average epicentral distance of 175 ± 5 km southwest of Edmonton for 40 of these events. Because Sn was not clear on the remainder, it was not possible to get focal depths for all the events.Seismic moments of 80 events with local magnitudes from 1.6 to 3.5 were found to be in the range of 6.6 ± 2 × 1018 to 7.9 ± 2 × 1020 dyn∙cm (6.6 ± 2 × 1013 to 7.9 ± 2 × 1015 N∙cm). A relationship between local magnitude and seismic moment was log (M0) = 1.3ML + 16.6. This is similar to that determined for California. Source radii, where they could be determined, were 500 ± 50 m and stress drops were 0.75 ± 0.75 bar (75 ± 75 kPa).The energy release of 263 events recorded at EDM from the Rocky Mountain House area was 5.6 × 1017 erg (5.6 × 1010 J). The b value for this earthquake swarm was 0.8, similar to that observed in other parts of western Canada.The depths of focus, the low stress drops, and the statistical similarity to other natural earthquake sequences suggest that at least part of the swarm is of a natural origin.

scholarly journals Source Parameter of Earthquakes in Talala, Gujarat (India): An Implication towards Seismotectonic

Proceedings ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 7
Author(s):  
Sandeep Kumar Aggarwal
Keyword(s):  
Epicentral Distance ◽  
Moment Tensor ◽  
Source Parameters ◽  
Focal Depth ◽  
B Value ◽  
Complete Sequence ◽  
P Value ◽  
Centroid Moment Tensor ◽  
North East ◽  
Lateral Plane

Talala is an excellent example of triggered neo-tectonic seismicity between two dams during a monsoon. An earthquake of Mmax 5.1 on 6 November 2007 at 21.16° N; 70.54° E, with a focal depth of 4.5 km and complete sequence, was first-time recorded on the latest broadband sensor. This found a dam/monsoon-induced earthquake preceded by 18 foreshocks of 2 ≤ Mw ≤ 4.8 within 9 h 11 minute, as well as smaller shocks that may not have been recorded because of sparse network coverage. After the deployment of local mobile observatories, aftershocks of Mw ≥ 1.0, which continued for months and subsided to background seismicity after four months, were recorded. The same kind of phenomena repeated, with Mmax 5.0 on 20 October 2011 at 21.06° N; 70.50° E, focal depth 5.5 km, which implies that the potential to generate dam/monsoon-induced seismicity took nearly four years again. These phenomena continued and the sequence was recorded by a network of 10 broadband seismographs (three in the Talala area and seven at an epicentral distance of 30 to 300 km). Centroid Moment Tensor (CMT) solutions and spectral source parameters of mainshock and aftershocks are evaluated to understand the seismotectonic of the region. The CMT depicts a major strike-slip motion along East North East-West South West with a left-lateral plane at 4.5 km depth. This indicates a sympathetic fault extension of the Son-Narmada fault. The source parameters of 400 shocks of Mw 1.0 to 5.1 found seismic moment 1011 to 1016.5 N-m, source radii 120–850 meter, and a stress drop of 0.003 to 25.43 Mpa. The b-value, p-value, fractal dimension, and slip on estimated different faults. The comparison between Talala and Koyna dam-induced source parameters tries to establish a comparison of seismicity from different parts of the world.

Source parameters from shallow events in the Rocky Mountain House earthquake swarm

1982 ◽  
Vol 19 (5) ◽  
pp. 907-918 ◽  
Author(s):  
C. J. Rebollar ◽  
E. R. Kanasewich ◽  
E. Nyland
Keyword(s):  
Source Parameters ◽  
Earthquake Swarm ◽  
Spectral Characteristics ◽  
High Stress ◽  
Rocky Mountain ◽  
P Wave ◽  
Digital Data ◽  
Integration Scheme ◽  
S Wave ◽  
Time Domains

We report here source parameters of the Rocky Mountain earthquake swarm derived from three-component digital data. During 6 days in October 1980, 21 events were recorded. Focal depths for these events are in the range of 1 ± 0.8 to 2 ± 2 km. Eleven events with local magnitudes from 2.1 to 2.8 yielded source parameters. Corner frequencies of the S-wave spectra were found in the range 6.2 ± 0.5 Hz, giving source dimensions of 160 ± 10 m. The corresponding P-wave corner frequencies are in the range 8.6 ± 3 Hz. The ratio of P to S corner frequencies varies from 0.9 to 2.1. There is a path effect between 13 and 16 Hz that could have affected these ratios. The average falloff over three components at high frequencies varies from −1.8 to −2.3. High stress drops, ranging from 47 to 263 bar (4.7–26.3 MPa), and apparent stresses, from 2.5 to 23 bar (0.25–2.3 MPa), were calculated. Five events have remarkably similar characteristics in the frequency and time domains. For these events the ratio of minimum strain energy W0, according to Kanamori, to the energy calculated using the integration scheme of Hanks and Thatcher was 3.7 ± 0.5. A theoretical value gives 3.1. The seismic efficiency ranges from 0.2 ± 0.04 to 0.17 ± 0.8. Large seismic moments for relatively small magnitudes were found. Some of these spectral characteristics are best explained as the result of displacement along a smooth fault.

Source parameters and scaling relationships of small earthquakes in the northeastern Caribbean

1981 ◽  
Vol 71 (4) ◽  
pp. 1173-1190
Author(s):  
Arthur Frankel
Keyword(s):  
Seismic Moment ◽  
Dynamic Stress ◽  
Source Parameters ◽  
Earthquake Swarm ◽  
Fold Increase ◽  
Virgin Islands ◽  
Scaling Relationships ◽  
Short Period ◽  
Relative Stress ◽  
Stress Drops

abstract The seismic moments and stress drops of 23 earthquakes (1.1 ≦ M ≦ 2.4) that occurred during an earthquake swarm in the Virgin Islands were determined from the analysis of their P waveforms. The data consist of digitally recorded seismograms collected by a short-period seismic network operating in the northeastern Caribbean. The events of the swarm are particularly useful for comparing the relative stress drops of small earthquakes, because their source to receiver paths and focal mechanisms are very similar. The static stress drops calculated for these earthquakes varied from about 0.2 to 2 bars. The data clearly illustrate that the static and dynamic stress drops of these earthquakes generally increased with the size (moment) of the events. The fault radii for these shocks increased with seismic moment, but only by a factor of 2 for a 100-fold increase in seismic moment. The velocity waveforms of the larger events were systematically more impulsive than those of the smaller earthquakes. These observations imply that, for this set of earthquakes, the final fault radius is a function of the stress drop that occurs during the rupture process.

Source parameters of the Ensenada Bay earthquake swarm, Baja California, Mexico

1985 ◽  
Vol 22 (1) ◽  
pp. 126-132 ◽  
Author(s):  
Cecilio J. Rebollar
Keyword(s):  
Seismic Data ◽  
Strain Energy ◽  
High Strain ◽  
Source Parameters ◽  
Earthquake Swarm ◽  
Ground Displacement ◽  
Source Dimensions ◽  
Fault Type ◽  
Stress Drops ◽  
High Strain Energy

Seismic data collected from the Ensenada Bay earthquake swarm of late 1981 were used to calculate the spectra of ground displacement. Data from the stations of Ensenada (ENX) and Cerro Bola (CBX), at epicentral distances of 14 and 57 km, respectively, were used to evaluate source parameters. The focal depths determined for these events were less than 10 km. The focal mechanism was a strike-slip fault type, with the plane of motion striking N52°W, parallel to the Agua Blanca Fault. Seismic moments ranging from 3.44 × 1019 to 5.99 × 1020 dyn∙cm (3.44 × 1014 to 5.99 × 1015 N∙cm) were estimated for events with local magnitudes in the range 1.7–2.3. The source dimensions were found to be 186 ± 36 m and the stress drops between 3 and 66 bar (0.3 and 6.6 MPa), comparable to results obtained in previous studies of shallow events (depths <10 km). The Ensenada swarm could be attributed to a localized zone of high-strain energy at the intersection of two faults. Ratios of P to S corner frequencies were evident for only five events; they were 1.39 ± 0.38. Magnitude and seismic moment from other studies were compared with the Ensenada data in the range of magnitudes 0–3. All the data can be accommodated by log M0 = 1.5 ML + (16.9 ± 1.1). The Ensenada earthquake swarm and the Victoria earthquake swarm, which occurred in the Mexicali valley in 1978, have similar source radii and corner frequencies for the same range of seismic moments.

Source parameters of the June 13, 1967 earthquake near Lake Ontario, New York State

1977 ◽  
Vol 14 (11) ◽  
pp. 2651-2657 ◽  
Author(s):  
Michio Hashizume ◽  
Nagakoto Tange
Keyword(s):  
New York ◽  
Surface Wave ◽  
Epicentral Distance ◽  
Source Parameters ◽  
New York State ◽  
Focal Depth ◽  
Lake Ontario ◽  
Strike Slip ◽  
York State ◽  
Long Period

Source parameters of an earthquake with magnitude mb = 4.4 were determined by using surface waves. Small but clear surface wave signals were observed on long period records gathered from seismograph stations within an epicentral distance of about 2000 km. The focal mechanism was determined to be of strike-slip type with the maximum and the minimum compression axes trending NNW–SSE and ENE–WSW, respectively. The focal depth was determined to be near either 3 or 20 km.

scholarly journals Earthquake swarm activity in south Gujarat

MAUSAM ◽  
2021 ◽  
Vol 42 (1) ◽  
pp. 89-98
Author(s):  
D. T. RAO ◽  
B. B. JAMBUSARIA ◽  
SANJAY SRIVASTAVA ◽  
N. P. SRIVASTAVA ◽  
ABDUL HAMID ◽  
...  
Keyword(s):  
Hot Springs ◽  
Earthquake Swarm ◽  
Focal Depth ◽  
Velocity Model ◽  
Atmospheric Temperature ◽  
B Value ◽  
New Delhi ◽  
Western Coast ◽  
Earthquake Activity ◽  
Peninsular India

South Gujarat, a part of western coast of Indian Peninsula started experiencing earth tremors of mild intensity since early February 1986. The shocks were widely felt with rumbling sound in these areas. More than 23000 micro earthquakes have since been recorded tilt December 1988, with a major event, ML=4.6 which occurred on.27 April.1986: In view of the location of multi-purpose projects like Ukai, Damanganga, .Jhuj, Kflia etc the monitoring this activity was Immediately started through a network of seven temporary- microearthquake recording stations. This was followed by various other studies such as geodetic, geomagnatic, radon gas monitoring and temperature measurements 9f hot springs. The Unai and Mola-Amba hot springs situated in this area have indicated the temperature of about 57oC and 37°C respectively against the normal atmospheric temperature of 33o C.   The analysis by Hypo- 71 program on IBM computer of India Met. Dep., New Delhi, using a velocity model  Koyna region has shown a well concentrated seismic activity over area of 7x 10 km2 and focal depth of 1-15 km. Clear migration of the activity has been observed. The activity which concentrated around Kella dam m early February-April 1986 migrated up to 18km to its south and back again to the religion around Kelia reservoir, by September 1987 with depth of foci progressively becoming shallower towards north .The 'b" value of 1.04 is higher than that of a few tectonic sequences of Peninsular India. The rate of decay of the activity was 0.52 which is rather slow compared to other sequences of the region. Hence, the reactivation of the existing fracturies/lineaments might be responsible or the recent activity. The geomagnetic studies in this area have corroborated tile existence of  NW-SE to NNE-SSW trending conductive fractures. The earthquake activity during 1988 is quite low compared  to earlier years.  

scholarly journals A Shallow Earthquake Swarm Close to Hydrocarbon Activities: Discriminating between Natural and Induced Causes for the 2018–2019 Surrey, United Kingdom, Earthquake Sequence

2019 ◽  
Vol 90 (6) ◽  
pp. 2095-2110 ◽  
Author(s):  
Stephen P. Hicks ◽  
James Verdon ◽  
Brian Baptie ◽  
Richard Luckett ◽  
Zoë K. Mildon ◽  
...  
Keyword(s):  
Source Parameters ◽  
Earthquake Swarm ◽  
Sedimentary Basins ◽  
B Value ◽  
Earthquake Sequence ◽  
Fault System ◽  
Current Evidence ◽  
Maximum Magnitude ◽  
Earthquake Parameters ◽  
Industrial Activities

ABSTRACT Earthquakes induced by subsurface industrial activities are a globally emotive issue, with a growing catalog of induced earthquake sequences. However, attempts at discriminating between natural and induced causes, particularly for anomalously shallow seismicity, can be challenging. An earthquake swarm during 2018–2019 in southeast England with a maximum magnitude of ML 3.2 received great public and media attention because of its proximity to operating oilfields. It is therefore vital and timely to provide a detailed characterization of the earthquake sequence at present, and to decide based on current evidence, whether the earthquakes were likely natural or induced. We detected 168 low‐magnitude earthquakes and computed detailed source parameters of these events. Most earthquakes occurred at a shallow depth of 2.3 km, >1  km deeper than the geological formations targeted by the oilfields, and laterally >3  km away from the drill sites. We combine the east–west‐trending cluster of the seismicity with 2D seismic reflection profiles to find the causative fault system for the earthquakes. A b‐value close to unity and strike‐slip faulting mechanisms are consistent with tectonic reactivation along a pre‐existing fault. Overall, we find no indicators in the earthquake parameters that would strongly suggest an induced source. Nor do we find any clear trends between seismicity and drilling activities based on operational logs provided by the operators. Injected volumes are near zero and monthly production amounts are many orders of magnitude smaller than other reported cases of extraction‐induced seismicity. On balance, and based on the available evidence, we find it currently unlikely that nearby industrial activities induced the seismic swarm. Most likely, the Surrey earthquakes offer a uniquely detailed insight into shallow seismicity within sedimentary basins. Nevertheless, self‐reporting of injection and production times and volumes by operators, and the lack of easily and publicly available oilfield operational data continues to be a point of concern for local residents.

Second hyperpolarizability of multimetallocenes [Cp–Mn–Cp] of Be, Mg and Ca

2015 ◽  
Vol 14 (01) ◽  
pp. 1550002 ◽  
Author(s):  
Kaushik Hatua ◽  
Prasanta K. Nandi
Keyword(s):  
Charge Transfer ◽  
Theoretical Study ◽  
Small Variation ◽  
Cooperative Effect ◽  
Second Hyperpolarizability ◽  
Nlo Property ◽  
Metal Atoms ◽  
Bonding Interaction ◽  
Charge Transfer Transitions ◽  
The Difference

Multimetallocene complexes ( Cp – M n– Cp ) of Be , Mg and Ca have been considered for the theoretical study of static second hyperpolarizability using a number of DFT functionals. Owing to the cooperative effect in bonding, beryllium forms multiberyllocene complexes ( Cp – Be n– Cp ) which have sufficient thermal stability with respect to dissociation into neutral fragments up to n = 10. On the other hand, multimetallocene complexes of Mg and Ca are found to be stable for n ≤ 5 which may be due to the weaker covalent bonding interaction between the larger metal atoms. The rather small variation of linear and cubic polarizabilities of Cp – Be n– Cp complexes beyond n = 5 arises from the rather weaker charge transfer transitions. The difference in NLO property among the investigated metal complexes arises from the extent of charge transfer from the terminal metal atoms and the distance between them. The charge transfer at longer distances in the ground state of Mg and Ca complexes leads to more intense electronic transition — the spectroscopic parameters of which strongly favors the enhancement of second hyperpolarizability.

Strong ground motion of mine tremors: Some implications for near-source ground motion parameters

1981 ◽  
Vol 71 (1) ◽  
pp. 295-319
Author(s):  
A. McGarr ◽  
R. W. E. Green ◽  
S. M. Spottiswoode
Keyword(s):  
Ground Motion ◽  
Source Parameters ◽  
Seismic Source ◽  
Shear Velocity ◽  
Recording System ◽  
Ground Acceleration ◽  
Hypocentral Distance ◽  
Earthquake Size ◽  
Mine Tremors ◽  
Stress Drops

abstract Ground acceleration was recorded at a depth of about 3 km in the East Rand Proprietary Mines, South Africa, for tremors with −1 ≦ ML ≦ 2.6 in the hypocentral distance range 50 m &lt; R ≦ 1.6 km. The accelerograms typically had predominant frequencies of several hundred Hertz and peak accelerations, a, as high as 12 g. The peak accelerations show a dependence on magnitude, especially when expressed as dynamic shear-stress differences, defined as σ˜ = ρRa, where ρ is density. For the mine tremors, σ˜ varies from 2 to 500 bars and depends on magnitude according to log σ˜ = 1.40 + 0.38 · ML. Accelerograms for 12 events were digitized and then processed to determine velocity and, for seven events with especially good S/N, displacement and seismic source parameters. Peak ground velocities v ranged up to 6 cm/sec and show a well-defined dependence one earthquake size as measured by ML or by seismic moment, Mo. On the basis of regression fits to the mine data, with −0.76 ≦ ML ≦ 1.45, log Rv = 3.95 + 0.57 ML, where Rv is in cm2/sec, and log Rv = −4.68 + 0.49 log Mo. These regression lines agree excellently with the corresponding data for earthquakes of ML up to 6.4 or Mo to 1.4 × 1026 dyne-cm. At a given value of ML or Mo, a, at fixed R, shows considerably greater variation than v and appears to depend on the bandwidth of the recording system. The peak acceleration at small hypocentral distances is broadly consistent with ρRa = 1.14 Δτrofs/β, where Δτ is stress drop, ro is the source radius, β is shear velocity, and fs is the bandwidth of the recording system. The peak velocity data agree well with Rv = 0.57 βΔτro/μ, where μ is the modulus of rigidity; both expressions follow from Brune's model of the seismic source and were compared with data for events in the size range 5 × 1016 ≦ Mo ≦ 1.4 × 1026 dyne-cm. Measurements of the source parameters indicated that, as for earthquakes, the stress drops for the tremors range from 1 to 100 bars and show no consistent dependence on Mo down to Mo = 5 × 1016 dyne-cm.

Focal mechanism and source depth of earthquakes from body- and surface-wave data

1971 ◽  
Vol 61 (5) ◽  
pp. 1369-1379 ◽  
Author(s):  
Nezihi Canitez ◽  
M. Nafi Toksöz
Keyword(s):  
Surface Wave ◽  
Body Wave ◽  
Source Parameters ◽  
Focal Depth ◽  
Spectral Ratio ◽  
The Body ◽  
Spectral Ratios ◽  
Motion Data ◽  
Wave Data ◽  
Surface Wave Data

abstract The determination of focal depth and other source parameters by the use of first-motion data and surface-wave spectra is investigated. It is shown that the spectral ratio of Love to Rayleigh waves (L/R) is sensitive to all source parameters. The azimuthal variation of the L/R spectral ratios can be used to check the fault-plane solution as well as for focal depth determinations. Medium response, attenuation, and source finiteness seriously affect the absolute spectra and introduce uncertainty into the focal depth determinations. These effects are nearly canceled out when L/R amplitude ratios are used. Thus, the preferred procedure for source mechanism studies of shallow earthquakes is to use jointly the body-wave data, absolute spectra of surface waves, and the Love/Rayleigh spectral ratios. With this procedure, focal depths can be determined to an accuracy of a few kilometers.

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