| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Dineva, Savka
(author)
-
Eastern Section 2008 meeting
- 2009
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 80:1, s. 159-160
-
Journal article (other academic/artistic)
|
|
| 5. |
- Dineva, Savka, et al.
(author)
-
Energy magnitude : A case study for southern Ontario/western Quebec (Canada)
- 2009
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 80:1, s. 136-148
-
Journal article (peer-reviewed)abstract
- The conventional methods for rapid determination of earthquake magnitude are based mainly on peak-to-peak amplitudes of specific phases on a seismic trace. Today, broadband digital records are readily accessible in real time, enabling the use of more information from a seismogram for rapid magnitude calculation. The aim of this work is to introduce a new magnitude scale for routine seismological analysis, denoted ME (P-wave, S-wave+coda, or both). This magnitude scale uses the signal energy and is illustrated here with a case study from southern Ontario/western Quebec (Canada). Traditional types of magnitude scales, based on the estimated maximum velocity (mb) and Richter local magnitude (ML), as well as the moment magnitude (MW), and some other magnitude types, based on the coda energy (MCoda) and ehvelope area (MEnv) are also computed for the study area for comparative purposes. Ihe proposed approach employed for this study can be easily applied to any other region of the world. The developed automatic procedure allowed the simultaneous computation of different magnitudes and different trace components and types of waves. The data used for this research are from 238 well-recorded earthquakes between 1991 and 2006 in southern Ontario/western Quebec/northern Ohio/northern NY State (1.0 < mN < 5.5). The results of our work show that, in general, magnitude values based on signal energy ME give less scattered estimates than magnitude values based on peak-to-peak measurements. We recommend using ME (S + coda) scale (vertical component) for quantifying the earthquakes in the study area in the future. The magnitude formula for this scale is given by ME = 0.5log ẼS + 0.92logD + 3.56 + S, where ẼS is the signal energy defined here (∑vs2 Δt, vS is measured in mm/s, Δt is the sample interval in seconds), D is the epicentral distance in km, and S is the station correction. The new ME magnitude can be used for a quick estimate of the MW magnitude for the study region using the relationship: MW = ME - 0.51 (for earthquakes with ME ≥ 2.6), obtained here.
|
|
| 6. |
|
|
| 7. |
- Dineva, Savka, et al.
(author)
-
Georgian Bay (Ontario) earthquake with magnitude m (sub N) 4.3 (October 20, 2005) and its foreshock-aftershock sequence; : tectonic implications
- 2006
-
In: Seismological Research Letters. - 0895-0695 .- 1938-2057. ; 77:2, s. 294-
-
Journal article (peer-reviewed)abstract
- On October 20 2005 at 21:16 GMT, a magnitude mN 4.3 earthquake occurred in the southern part of Georgian Bay, approximately 12 km north of Thornbury, Ontario, Canada (latitude 44.67° N and longitude 80.46° W). This earthquake is the largest one in southern Ontario recorded by a local seismograph network and is of particular interest due to its location 90 km from a proposed long-term storage facility for high-level nuclear waste. The earthquake was felt along the southern shore of Georgian Bay with maximum intensity of IV MM. During the first 24 hours after the earthquake occurred, four portable ORION seismograph systems were installed to record possible aftershocks. The main shock on October 20 2005 was preceded by a foreshock 30 sec before it, and was followed by 5 aftershocks within 4-day period. All the epicenters of the foreshock and aftershocks were within 2.5 km from the epicenter of the main shock. The large amount of available data from the recently installed broad-band POLARIS seismograph stations, as well as the permanent CNSN stations and the temporary stations, gave us a unique opportunity to study the parameters of this event. The analysis of the foreshock-main shock-aftershock sequence indicated focal depths around 7 to 12 km. The focal mechanism calculated from the polarities of P-arrivals showed predominantly thrust mechanism of the main shock, with nodal planes oriented almost NW-SE. The focal mechanism is very similar to the predominant focal mechanism of the earthquakes in Western Quebec Seismic Zone but different from the predominant strike-slip focal mechanisms south of Lake Erie and the oblique slip mechanisms in western Lake Ontario. Aeromagnetic data reveal a prominent NW-SE structural fabric for the basement rocks beneath Georgian Bay, in good agreement with the orientation of the nodal planes. This structural fabric probably reflects mafic dykes (the Matachewan dyke swarm). The spectra of S-waves, recorded at 13 bedrock stations, were fitted with Brune’s model and used to calculate the seismic moment (3.6e+14 N.m), source radius (~ 400 m), stress drop (~ 20 bars), and moment magnitude (Mw 3.7). This seismic moment and calculated focal mechanism were used as initial approximation for seismic moment tensor inversion. The results of the inversion showed correspondence between the seismic moment and double-couple focal mechanism calculated from the moment tensor
|
|
| 8. |
- Dineva, Savka, et al.
(author)
-
High Precision Magnitude Measurements Using Total Signal Energy of P- and S-Wave Trains
- 2007
-
In: Seismological Research Letters. - 0895-0695 .- 1938-2057. ; 78:2, s. 249-250
-
Journal article (peer-reviewed)abstract
- The conventional methods for determining the magnitude of an earthquake such as Richter magnitude, Nuttli magnitude etc. are based mainly on peak-to-peak amplitudes of different phases on the seismic trace. These magnitude scales were developed in the past during the days when we had only paper seismic recordings. The conventional method for determining moment magnitude obtained from seismic moment is measured actually as the low frequency level of the displacement spectrum. Both of the above mentioned methods ignore a lot of the information, which is provided in a modern digital 3-component seismogram. In this study we explore the applicability of total signal energy as the main parameter to be used in magnitude estimation. Over 2100 three-component seismic traces from 258 local and regional earthquakes recorded on the Southern Ontario Seismic /POLARIS networks were used in this study. To relate the new energy magnitude scale to the old ones, including Mw, we have calculated most known magnitude types and the seismic moment of the earthquakes. To carry out this work, an automatic procedure was developed for measuring the peak-to peak amplitudes, periods, duration, and signal energy for each seismic trace. For calculation of the seismic moment, an iterative technique was developed to separate the effects of source functions from site response and geometrical spreading and attenuation effects. We have compared our energy magnitude measurements with the other well-known magnitude measurements by monitoring the solution errors. Our results show that the measurements of total seismic signal energy in both the P- and S-wave trains can improve the precision of the earthquake magnitude significantly and reduce much of the scatter found in conventional magnitude measurements.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Ferrario, Maria Francesca, et al.
(author)
-
Developing the First Intensity Prediction Equation Based on the Environmental Scale Intensity : A Case Study from Strong Normal-Faulting Earthquakes in the Italian Apennines
- 2020
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 91:5, s. 2611-2623
-
Journal article (peer-reviewed)abstract
- Earthquakes produce effects on the built and natural environment, the severity of which decays with distance from the epicenter. Empirical relations describing the intensity attenuation with distance are fundamental for seismic hazard assessment and for deriving parameters for preinstrumental events. Seismic intensity is usually assigned based on damage to buildings and infrastructures; this can be challenging for intensity degrees higher than X or when macroseismic fields of multiple events close in time are overlapping. A complementary approach is the study of earthquake environmental effects (EEEs), which are used to assign intensity on the environmental scale intensity (ESI) scale. However, a quantitative comparison between the ESI and traditional scales, and an equation describing the ESI attenuation with distance are still lacking. Here, we analyze 14 historical and instrumental events (time window 1688–2016) in the central and southern Apennines (Italy), comparing ESI and Mercalli–Cancani–Sieberg (MCS) intensities. Our results show that ESI consistently provides higher intensity near the epicenter and the attenuation is steeper than MCS. We derive the first intensity prediction equation for the ESI scale, which computes local intensity as a function of distance and epicentral intensity value. We document that, in the near field, the MCS attenuation for shallow crustal events occurred in the twenty-first century is steeper than previous events, whereas the ESI attenuation shows a consistent behavior through time. This result questions the reliability of current empirical relations for the investigation of future events. We recommend including EEEs in intensity assignments because they can guarantee consistency through time and help in evaluating the spatial and temporal evolution of damage progression during seismic sequences, thus ultimately improving seismic risk assessment.
|
|
| 17. |
- Gibbons, Steven J., et al.
(author)
-
The European Arctic : A Laboratory for Seismoacoustic Studies
- 2017
-
In: Seismological Research Letters. - : Center for Open Science. - 0895-0695 .- 1938-2057.
-
Journal article (peer-reviewed)abstract
- We describe the seismoacoustic monitoring network in Fennoscandia and North West Russia and present how it is being used to characterize infrasound studies in that part of the world. The history of the infrasound array network is presented, together with a description of array processing considerations, and examples of infrasound signals recorded from repeating explosions.
|
|
| 18. |
|
|
| 19. |
- Joshi, Niranjan, et al.
(author)
-
Earthquake disaster fatality data: Temporally stable power-law behavior and effects of underreporting
-
In: Seismological Research Letters. - 0895-0695 .- 1938-2057.
-
Journal article (peer-reviewed)abstract
- We investigate changes in the global reported fatalities from earthquake disasters in theleading global disaster database EM-DAT. Drawing parallels with the Gutenberg-Richterfrequency-magnitude analysis, in terms of disaster frequency versus the number of casual-ties, we see a significant overlap of the curves and improving levels of completeness oversix 20-year periods. This implies a decrease in underreporting with time. We find that theapparent strong upwards trend in the number of (reported) earthquake disasters in EM-DATis caused by a gradually improved reporting primarily of events killing fewer than 10 peo-ple. An implication of our findings is that the true (reported and unreported) number ofearthquake disasters, according to the EM-DAT definition, has been surprisingly constantover, at least, the last 100 years. We also show that the average annual number of peoplekilled in earthquake disasters is relatively unaffected by spurious trends in reporting, and hasremained remarkably constant, at least since the 1960s, despite population increase.
|
|
| 20. |
- Kim, WonYoung, et al.
(author)
-
The 4 August 2004, Lake Ontario, earthquake
- 2006
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 77:1, s. 65-73
-
Journal article (peer-reviewed)abstract
- A Mw 3.1 earthquake occured in Lake Ontario along the United States-Canada border, about 30 km south from Port Hope, Ontario, Canada, on 4 August 2004. Despite its small size, the shock was very well recorded by broadband seismographic stations deployed in recent years in Ontario, Canada, and in New York State. More than 40 broadband stations at local and regional ranges provided high-quality digital data. Waveform data analysis constrained the source at a depth of 4 (±2) km, which places the shock in the shallow Precambrian basement beneath Paleozoic platform deposits. The source mechanism from the regional waveform inversion for the double-couple moment tensor is predominantly strike-slip faulting. A NS striking (8°) nodal plane dipping to the east (dip = 59°) is the likely fault plane which represents right-lateral strike-slip motion. The subhorizontal P-axis orientation (trend = 234° and plunge = 12°) is consistent with the maximum horizontal compressional stress (SHmax) direction in eastern North America. Although the 4 August 2004 event is a small shock and has the seismic moment of M0 = 4.45 (±2.30) × 1013 Nm, it is the largest instrumentally recorded earthquake that has occurred in Lake Ontario. This and other significant earthquakes in the region suggest a broad-scale strike-slip faulting stress regime with a shallow seismogenic layer in the Erie-Ontario Lowlands region. The shallow focal depths of earthquakes in the region increase the risk of higher ground shaking compared to other seismic zones in northeastern North America with a deeper seismogenic layer.
|
|
| 21. |
- Lund, Björn, 1965-, et al.
(author)
-
The Modern Swedish National Seismic Network : Two Decades of Intraplate Microseismic Observation
- 2021
-
In: Seismological Research Letters. - : SEISMOLOGICAL SOC AMER. - 0895-0695 .- 1938-2057. ; 92:3, s. 1747-1758
-
Journal article (peer-reviewed)abstract
- The Swedish National Seismic Network (SNSN) was modernized and rapidly expanded during the period 1998?2012. The network currently operates 68 permanent seismic stations, all with broadband instruments supplying real-time continuous data at 100 samples per second. Continuous data from 10 stations are shared with the international community via Orfeus, and approximately 10 stations of their individual choice are shared with institutes in neighboring countries (Denmark, Finland, Norway, and Germany). The SNSN uses the South Iceland Lowland (SIL) system as the primary system for automatic detection and event definition. In addition, an in-house system based on migration and stacking is used for automatic detection of small events, and implementations of SeisComP (SC) and Earthworm are used primarily for rapid detection of larger regional events. Global monitoring is performed with SC, using approximately 250 global stations, and we operate a continuous rapid risk assessment system serving Swedish crisis management authorities. Since the start of automatic processing in August 2000, the SNSN has recorded and interactively analyzed more than 171,000 seismic events, of which 10,700 were earthquakes with local magnitudes ranging from around ?1 to 4.3. The microearthquake activity detected in the last 20 yr has significantly improved the identification and understanding of seismically active structures in Sweden.
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
- Mantyniemi, Paivi B., et al.
(author)
-
A Reappraisal of the Luroy, Norway, Earthquake of 31 August 1819
- 2020
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 91:5, s. 2462-2472
-
Journal article (peer-reviewed)abstract
- Archives and libraries were visited to find previously unknown documents testifying to the Luroy, Norway, earthquake of 31 August 1819 in northernmost continental Europe. The focus here is on Sweden, Finland, and Russia, which are important for determining the area of perceptibility east of Norway. The new written sources include 12 notes or entries in original archived documents, six contemporary newspaper reports, and two recollections written down years later. The original documentation uncovered is contributory to establishing the authenticity of the observations in Finland and Sweden. The dates of the original documentation allow tracing of the dissemination of eyewitness accounts in writing from the inner area of perceptibility southward to the larger documentation and population centers. New sources of information include weather reports of the Royal Swedish Academy of Sciences, minutes of its meetings, and correspondence sent to the Senate in Finland. The minutes of meetings of the Academy indicate that ample data were collected in the Swedish province of Vasterbotten. We found no original Russian documentation but uncovered national newspapers that are more reliable than the previously used Parisian newspaper. To increase transparency, we provide the first list of macroseismic data points (MDPs) including the respective documentation that testify to the Luroy earthquake. A macroseismic intensity was assigned to a locality, using the European Macroseismic Scale of 1998, when adequate information was available. Accounting for the uncertainty of intensity assessment, the magnitude was estimated as moment magnitude M = 5.9 +/- 0.2, reconfirming the ranking as the largest onshore or nearshore earthquake in the historical seismicity record of Fennoscandia. In addition to the reappraisal of the 31 August 1819 earthquake, a macroseismic map is provided for the earthquake of 17 February 1819, which was felt in northern Finland and Sweden. Some of its MDPs were previously associated with the Luroy earthquake.
|
|
| 25. |
- Mereu, Robert F., et al.
(author)
-
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
- 2013
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 84:5, s. 899-916
-
Journal article (peer-reviewed)abstract
- 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. The key results of our paper: (1) there is no unique pair of values of the coefficients Q(0) and n of the frequency-dependent Quality factor relationship Q=Q(0)f(n), but there exist pairs of Q(0) and n along a curve in Q(0)-n space that are equivalent in terms of their effect on spectral shape; (2) the 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) the relation between moment magnitude M and energy magnitude M-E was found to be M = 8/9 M-E.
|
|
| 26. |
- Mereu, R.F., et al.
(author)
-
The Seismicity of the Western Lake Ontario Area : Results from the Southern Ontario Seismic Network (SOSN), 1992-2001
- 2002
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 73:4, s. 534-551
-
Journal article (peer-reviewed)abstract
- The Southern Ontario Seismic Network (SOSN) consists of eleven three-component short-period seismic stations, located mainly in the Toronto-Hamilton-Niagara area of Ontario, Canada. The network has been in operation by the University of Western Ontario (UWO) for Ontario Power Generation (OPG) since 1991 with the purpose of obtaining information on the seismicity and seismic hazards of a region of southern Ontario in which a number of nuclear power stations are located. Over the past decade, an average of more than ten local earthquakes per year in the western Lake Ontario area was detected by the SOSN. Most of the events were in the 2–3 magnitude (MN) range. The largest events during this time took place in the surrounding regions—Pymatuning, northwestern Pennsylvania (285 km southwest from Toronto, just south of Lake Erie, 25 September 1998, MN 5.4), northern Ontario/Quebec border (325 km north of Toronto, 1 January 2000, MN 5.2), Ashtabula, Ohio (262 km southwest of Toronto, 26 January 2001, MN 4.4), and Au Sable Forks, New York (436 km east of Toronto, 20 April 2002, MN 5.1). The largest earthquake (MN 3.8) in the western Lake Ontario region during the past ten years occurred on 26 November 1999 in Lake Ontario, 16 km southeast of the town of Pickering, which lies just east of Toronto. The estimated location uncertainty (±2 km) is significantly better than that which was possible before 1991. The focal depths, though poorly constrained for most events, are shown to lie in the 3–15 km range, well within the Grenvillian rocks of the Precambrian Shield. The new seismicity map shows that a definite pattern is emerging in the SOSN data set in Lake Ontario, one which is significantly different from the past historical earthquake patterns obtained when the instrumental coverage was poor. Most events occur in scattered clusters in the western part of Lake Ontario and the northwestern corner of New York State. The area of seismicity does not extend significantly to the north of western Lake Ontario and appears to end to the west rather abruptly along a 30 km small fault line running from south of Hamilton in a north-northeasterly direction to Burlington, Ontario. Although the area of seismicity coincides with a region of linear magnetic anomaly trends (suggesting a strong structural fabric in the basement rocks), the correlation of seismicity of the new SOSN data set with magnetic lineaments is still unclear. The cause of the seismicity is speculated to be related to water flows along various fissures below the lake. It is known from induced seismicity studies of reservoirs that the presence of fluids can cause earthquakes by changing the pore pressure and reducing the friction along any faults which may be present. From seismic reflection studies, dipping structures and shear zones have been imaged to extend southeastward under Lake Ontario. This may explain why most of the earthquakes are occurring under the lake or southeast of the lake.
|
|
| 27. |
|
|
| 28. |
|
|
| 29. |
- Mihaylov, D., et al.
(author)
-
Site response effects and noise attenuation at the seismic stations of Bruce borehole network (Ontario, Canada)
- 2008
-
In: Seismological Research Letters. - 0895-0695 .- 1938-2057. ; 79:1
-
Journal article (peer-reviewed)abstract
- A three-station broadband network was installed around the Bruce Nuclear site at the beginning of August 2007, to monitor microearthquakes within a 50-km radius of the plant. The seismic network was equipped with borehole stations installed at cased boreholes at depths of 25, 27 and 40 m, and temporary surface stations at the same sites. The aim of the doubled identical equipment (Geotech Instruments' KS2000) was to compare the records of local, regional and teleseismic events, and seismic noise and to obtain results about the noise reduction, attenuation and the site response at each station. During the design and installation of the seismic network different geophysical surveys were carried out: refraction seismic profiles, vertical seismic profiling, and noise level measurements at different depths along the borehole. The obtained velocity models were used for modeling of the site response and finally comparison with the real data from the parallel borehole-surface recordings, and measured predominant frequencies using the Nakamura's HVSR method. The real noise reduction estimated from the parallel recordings was compared with the predicted 10 dB noise reduction. A practical conclusion was drawn out about the optimum borehole depths for instrument installation based on the noise reduction / attenuation balance and signal-to-noise ratio with the depth. The seismic threshold magnitude for the monitored area estimated at the design stage was compared with the threshold magnitude obtained from the real data.
|
|
| 30. |
- Nazeri, Sahar, et al.
(author)
-
Rapid Estimation of the Epicentral Distance in the Earthquake Early Warning System around the Tehran Region, Iran
- 2019
-
In: Seismological Research Letters. - : SEISMOLOGICAL SOC AMER. - 0895-0695 .- 1938-2057. ; 90:5, s. 1916-1922
-
Journal article (peer-reviewed)abstract
- The estimation of epicentral distance is a critical step in earthquake early warning systems (EEWSs) that is necessary to characterize the level of expected ground shaking. In this study, two rapid methodologies, that is, B-Delta and C-Delta , are evaluated to estimate the epicentral distance for use in the EEWSs around the Tehran region. Traditionally, the B and C coefficients are computed using acceleration records, however, in this study, we utilize both acceleration and velocity waveforms for obtaining a suitable B-Delta and C-Delta relationships for the Tehran region. In comparison with observations from Japan, our measurements fall within the range of scatter. However, our results show a lower trend, which can strongly depend on the few numbers of events and range of magnitude (small-to-moderate) of earthquakes used in the current research. To improve our result, we include some large earthquakes from Iran, Italy, and Japan with magnitude larger than 5.9. Although the optimal trend is finally obtained by fitting a line to the distance-averaged points, we conclude that the same trend and relationship as Japan can be used in Tehran early warning system. We also found that B and C parameters are strongly compatible to each other. As time windows of 3.0 and 0.5 s after the P onset are chosen respectively to compute the B and C values, so by selecting the C parameter as a proxy of B parameter to estimate the epicentral distance, we may save significant time in order of about 2.5 s in any earthquake early warning applications.
|
|
| 31. |
- Peltier, Aline, et al.
(author)
-
Volcano Crisis Management at Piton de la Fournaise (La Reunion) during the COVID-19 Lockdown
- 2021
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 1938-2057 .- 0895-0695. ; 92:1, s. 38-52
-
Journal article (peer-reviewed)abstract
- In March 2020, the coronavirus disease 2019 outbreak was declared a pandemic by the World Health Organization and became a global health crisis. Authorities worldwide implemented lockdowns to restrict travel and social exchanges in a global effort to counter the pandemic. In France, and in French overseas departments, the lockdown was effective from 17 March to 11 May 2020. It was in this context that the 2-6 April 2020 eruption of Piton de la Fournaise (La Reunion Island, Indian Ocean) took place. Upon the announcement of the lockdown in France, a reduced activity plan was set up by the Institut de Physique du Globe de Paris, which manages the Observatoire Volcanologique du Piton de la Fournaise (OVPF). The aim was to (1) maintain remote monitoring operations by teleworking and (2) authorize fieldwork only for critical reasons, such as serious breakdowns of stations or transmission relays. This eruption provided an opportunity for the observatory to validate its capacity to manage a volcanic crisis with 100% remotely operated monitoring networks. We thus present the longand short-term precursors to the eruption, and the evolution of the eruption recorded using the real-time monitoring data as communicated to the stakeholders. The data were from both continuously recording and transmitting field instruments as well as satellites. The volcano observatory staff remotely managed the volcano crisis with the various stakeholders based only on these remotely functioning networks. Monitoring duties were also assured in the absence of ad hoc field investigation of the eruption by observatory staff or face-to-face communications. The density and reliability of the OVPF networks, combined with satellite observations, allowed for trustworthy instrument-based monitoring of the eruption and continuity of the OVPF duties in issuing regular updates of volcanic activity in the context of a double crisis: volcanic and health.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Thybo, Hans, et al.
(author)
-
ScanArray : A Broadband Seismological Experiment in the Baltic Shield
- 2021
-
In: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 92:5, s. 2811-2823
-
Journal article (peer-reviewed)abstract
- The ScanArray international collaborative program acquired broadband seismological data at 192 locations in the Baltic Shield during the period between 2012 and 2017. The main objective of the program is to provide seismological constraints on the structure of the lithospheric crust and mantle as well as the sublithospheric upper mantle. The new information will be applied to studies of how the lithospheric and deep structure affect observed fast topographic change and geological‐tectonic evolution of the region. The program also provides new information on local seismicity, focal mechanisms, and seismic noise. The recordings are generally of very high quality and are used for analysis by various seismological methods, including P‐ and S‐wave receiver functions for the crust and upper mantle, surface wave and ambient noise inversion for seismic velocity, body‐wave P‐ and S‐wave tomography for upper mantle velocity structure using ray and finite frequency methods, and shear‐wave splitting measurements for obtaining bulk anisotropy of the upper and lowermost mantle. Here, we provide a short overview of the data acquisition and initial analysis of the new data, together with an example of integrated seismological results obtained by the project group along a representative ∼1800‐km‐long profile across most of the tectonic provinces in the Baltic Shield between Denmark and the North Cape. The first models support a subdivision of the Paleoproterozoic Svecofennian province into three domains, where the highest topography of the Scandes mountain range in Norway along the Atlantic Coast has developed solely in the southern and northern domains, whereas the topography is more subdued in the central domain.
|
|
| 35. |
- Mazinanian, Neda, et al.
(author)
-
Metal release and corrosion resistance of different stainless steel grades in simulated food contact
- 2016
-
In: Corrosion. - : NACE International. - 0010-9312 .- 1938-159X. ; 72:6, s. 775-790
-
Journal article (peer-reviewed)abstract
- A new technical guideline has been implemented by the Council of Europe (CoE) to ensure the stability and safety of food contact articles of metals and alloys, using 5 g/L citric acid (pH 2.4) and artificial tap water DIN 10531 (pH 7.5) as food simulants. The objectives of this study were: (i) to quantify the extent of metal release from austenitic (grades AISI 201, 204, 304, and 316L), ferritic (grades AISI 430 and EN 1.4003), and lean duplex stainless steel (grade EN 1.4162) in citric acid (5 g/L, pH 2.4) and in artificial tap water (pH 7.5); (ii) to compare the release of metals to the surface oxide composition, the open circuit potential-time dependence, and the corrosion resistance; and (iii) to elucidate the combined effect of high chloride concentrations (0.5 M NaCl) and citric acid at pH 2.2 and 5.5 on the extent of metal release from AISI 304 with and without prior surface passivation by citric acid. Exposures of all stainless steel grades in citric acid and artificial tap water up to 10 d (at 70°C/40°C) resulted in lower metal release levels than the specific release limits stipulated within the CoE protocol. For all grades, metals were released at levels close to the detection limits when exposed to artificial tap water, and higher release levels were observed when exposed to citric acid. Increased surface passivation, which resulted in reduced metal release rates with time, took place in citric acid for all grades and test conditions (e.g., repeated exposure at 100°C). There was no active corrosion in citric acid at pH 2.4. Fe (in citric acid) and Mn (in all solutions, but mostly tap water) were preferentially released, as compared to their bulk alloy content, from all stainless steel grades. Ni was released to the lowest extent. 0.5 M NaCl induced a very low (close to detection limits) metal release from grade AISI 304 at pH 5.5. When combined with citric acid (5 g/L) and at lower pH (2.2), 0.5 M NaCl induced slightly higher metal release compared to citric acid (pH 2.4) alone for coupons that were not pre-passivated. Pre-passivation in 5 g/L citric acid (pH 2.4) at 70°C for 2 h largely reduced this solution dependence. Pre-passivation resulted in an up to 27-fold reduced extent of metal release in solutions containing citric acid and/or NaCl at pH 2.2 to 5.5, and resulted in improved reproducibility among replicate samples.
|
|
