Savka Dineva

The Application of Velocity Spectral Stacking to Extract Information on Source and Path Effects for Small‐to‐Moderate Earthquakes in Southern Ontario with Evidence for Constant‐Width faulting

We analyzed over 3000 Fourier spectra from 370 earthquakes of energy magnitude ( M E) 1.1–6.0 recorded by the Southern Ontario Seismic Network (SOSN)/POLARIS networks during the period 1991–2010 in the area of southern Ontario and western Quebec. We employed a range of velocity stacking methods to significantly reduce the problem of variability due to wave scattering. This enabled us to determine underlying nonrandom spectral features, including source effects, site effects, and anelastic attenuation effects on spectral shape. The analysis technique is that we stack the velocity spectra of the whole observed data set into one or two bins and then compare that sum (the observed stack) with the theoretical expectation for corresponding stacks of simulated signals (the theoretical stack) for a given set of input parameters. A grid‐search technique is used to find the input‐parameter combination that optimizes the agreement between the observed and theoretical stacks. By stacking the spectra in different ways, different underlying spectral features are explored. We find the method works surprisingly well, allowing us to determine the apparent anelastic attenuation effects on the spectral shape, the average effect of site response, and some basic features of the source spectra.nnThe key results of our paper: (1)xa0there is no unique pair of values of the coefficients Q and n of the frequency‐dependent Quality factor relationship Q = Q f n , but there exist pairs of Q and n along a curve in Q – n space that are equivalent in terms of their effect on spectral shape; (2)xa0the relationship between log corner frequency and energy magnitude ( M E) is linear, with a slope close to (−0.22) that is consistent with constant‐width faulting for the studied small‐to‐moderate events; (3)xa0the relation between moment magnitude M and energy magnitude M E was found to be M =u2009u20098/9u2009u2009 M E.

Source parameters of seismic events potentially associated with damage in block 33/34 of the Kiirunavaara mine (Sweden)

Forty-six mining-induced seismic events with moment magnitude between −1.2 and 2.1 that possibly caused damage were studied. The events occurred between 2008 and 2013 at mining level 850–1350xa0m in the Kiirunavaara Mine (Sweden). Hypocenter locations were refined using from 6 to 130 sensors at distances of up to 1400 m. The source parameters of the events were re-estimated using spectral analysis with a standard Brune model (slope −2). The radiated energy for the studied events varied from 4.7xa0×xa010−1 to 3.8xa0×xa0107 J, the source radii from 4 to 110xa0m, the apparent stress from 6.2xa0×xa0102 to 1.1xa0×xa0106 Pa, energy ratio (Es/Ep) from 1.2 to 126, and apparent volume from 1.8xa0×xa0103 to 1.1xa0×xa0107 m3. 90% of the events were located in the footwall, close to the ore contact. The events were classified as shear/fault slip (FS) or non-shear (NS) based on the Es/Ep ratio (>10 or <10). Out of 46 events 15 events were classified as NS located almost in the whole range between 840 and 1360xa0m, including many events below the production. The rest 31 FS events were concentrated mostly around the production levels and slightly below them. The relationships between some source parameters and seismic moment/moment magnitude showed dependence on the type of the source mechanism. The energy and the apparent stress were found to be three times larger for FS events than for NS events.

Separation of High‐ and Low‐Level Ambient Noise for HVSR: Application in City Conditions for Greater Toronto Area

Abstract The Nakamura method, which involves horizontal‐to‐vertical spectral ratio (HVSR) analysis, is widely used for seismic microzonation studies. The noise from local traffic in city conditions presents a challenge for the application of HVSR analysis. This article presents a technique developed for separation of the transient noise due to local traffic (high‐level noise) and background ambient noise (low‐level noise) and the application of the HVSR analysis to both partitions of the noise. This approach is applied to identify the predominant frequencies for almost 200 noise samples from the Greater Toronto area. The results demonstrated that the developed technique is effective and allows estimation of the fundamental resonant frequency in the HVSR in urban environment, even in the presence of intensive nearby traffic. The interpretation of the obtained results showed that, most probably, the lower (fundamental) frequency appears due to multiple reflections from the overburden/bedrock boundary. In some cases, a resonance with higher amplitude is dominant, and it is due to a contrast boundary between soil layers in the overburden.

Kingston, Ontario, 5–7 October 2008

The 80th annual meeting of the Eastern Section of the Seismological Society of America took place in Kingston, Ontario, 5–7 October 2008. It was a well-attended meeting, with 75 registrants, 25 of them students. Fifty-one papers were presented, 36 oral and 15 by poster. There were three special sessions during the meeting: “Induced and Mining Seismicity” (eight papers), “The April 18, 2008, Southern Illinois Earthquake: Post Earthquake Studies” (two papers), and “Seismic Hazard Related to the Nuclear Industry” (12 papers). The rest of the presentations and posters were part of general sessions.nnEight oral presentations and seven posters were by students. The award for the best student oral presentation went to Alan Baird of Queens University in Kingston, Ontario, for his paper, “Stress chanelling and partitioning of seismicity in the Charlevoix seismic zone, Quebec, Canada.” His co-authors were Steve McKinnon and Laurent Godin. The awards for second- and third-best student papers went to Katie Ploeger (Carleton University, Ottawa, Ontario) and Kathryn Gunberg (Virginia Tech, Blacksburg, Virginia). The best poster presentation award was won by Ken MacPherson of University of Kentucky, Lexington, Kentucky, for his paper, “Strong ground motion in the Upper Mississippi Embayment from finite-fault, finite-difference simulations,” with co-authors Edward Woolery and Zhenming Wang. The awards for second- and third-best student posters went to Caitlin Latimer (University of Western Ontario, London, Ontario) and Leo Leon (University of Calgary, Calgary, Alberta).nnnnnn▴ The best oral presenters: Katie Ploeger (left), Alan Baird (middle), Kathryn Gunberg (right). Photo by S. Dineva. nnnnThe pre-meeting field trip had both a scientific part and a visit to wineries in Prince Edward County. Dr. Laurent Godin of Queens University led 23 participants to four geological stops north of Kingston, Ontario. At the first stop they were able to see evidence for the complex deformation and reactivation history …