On the reliability of PKIIKP phase identification at a single station

2021 ◽  
Author(s):  
Olga Usoltseva ◽  
Vladimir Ovtchinnikov
Keyword(s):  
Inner Core ◽  
Seismic Velocity ◽  
Seismic Station ◽  
Shear Velocity ◽  
Outer Core ◽  
Joint Analysis ◽  
Time Range ◽  
Model Parameters ◽  
Phase Identification ◽  
Single Station

<p><span>Study of the contact zone between the inner and outer core represents considerable interest for understanding of properties, structures and dynamic of the Earth's core. One of </span><span>the </span><span>sources of </span><span>the </span><span>data about the processes proceeding in the top part of the inner core is the seismic wave PKIIKP once reflected from an undersize inner core boundary. Amplitudes of these waves are sensitive to the shear velocity in the top part of the inner core and are small. Therefore their identification at a single seismic station is not reliable without application of additional methods of analysis. </span><span>Significant in this regard is the discussion about the source (in inner core or in mantle) of anomalous arrivals<!-- Это можно удалить --> detected at the TAM station in North Africa [1,2] in the time range of PKIIKP phase.</span></p><p><span>To estimate influence of model parameters (S and P seismic velocity) on the characteristics of PKIIKP wave (amplitude and travel time) we calculated sensitivity kernels for upper mantle and inner core for dominant period 1.2 s, azimuth step 0.2 degrees and radius step 20 km by using DSM Kernel Suite algorithm. It was revealed that PKIIKP amplitude is more sensitivities to mantle heterogeneities than to inner core ones. </span><span>For reducing the effects of the overlying structures we suppose to use </span>а <span>joint analysis PKIIKP and pPKIIKP waves. </span><span>With this approach, an incorrect i</span><span>dentification</span><span> of the PKIIKP wave is most likely excluded. </span><span>We<!-- Было бы хорошо привести пример --> demonstrate the effectiveness of the approach on the example of processing the seismogram of the 11.02.2015 earthquake re</span>с<span>o</span><span>rded at the GZH station in China at a distance of 179.4 degrees.</span></p><p><span>1. Wang W., Song X. Analyses of anomalous amplitudes of antipodal PKIIKP waves</span><span>,</span><span> E<!-- Удаляется вместе с текстом, выделенным выше Зеленым цветом. -->aPP. 2019. V. 3. P. 212-217. doi: 10.26464/epp2019023</span></p><p><span>2. Tsuboi S., Butler R. Inner core differential rotation inferred from antipodal seismic observations</span><span>,</span><span> PEPI</span><span>,</span><span> 2020. V.301. 106451. </span></p>

scholarly journals Rapid Detection and Location of Debris Flow Initiation at Illgraben, Switzerland

2016 ◽  
Author(s):  
Fabian Walter ◽  
Arnaud Burtin ◽  
Brian McArdell ◽  
Niels Hovius ◽  
Bianca Weder ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rapid Detection ◽  
Seismic Velocity ◽  
Data Communication ◽  
Ground Vibration ◽  
Detection Methods ◽  
Phase Identification ◽  
Processing Scheme ◽  
Single Station

Abstract. Heavy precipitation can suddenly mobilize tens to hundreds of thousands of cubic meters of sediments in steep Alpine torrents. The resulting debris flows (mixtures of water, sediments and boulders) move downstream with velocities of several meters per second and have a high destructive potential. Warning schemes for affected communities rely on raising awareness to the debris flow threat, precipitation monitoring and rapid detection methods. The latter, in particular, remain an ongoing challenge, because debris-flow-prone torrents have their catchments in steep and inaccessible terrain, where installing and maintaining instrumentation is difficult. Here, we propose a simple processing scheme for seismic network data. We use debris flow and noise seismograms from Illgraben, Switzerland, a torrent, which produces several debris flow events per year. Automatic in-situ detection is currently based on geophones mounted on concrete check dams and radar stage sensors hung above the channel. The proposed approach has the advantage that it uses seismometers, which can be installed at more accessible locations, and where a stable connection to portable phone networks is available for data communication. Our data processing uses time-averaged ground vibration amplitudes to estimate the location of the debris flow front. Applied to continuous data streams, inversion of the seismic amplitude decay eliminates the need for single-station-based detection and knowledge of the local seismic velocity model. This makes the approach suitable for automation, as seismic phase identification is unnecessary and the amplitude averaging significantly reduces data volume. We apply our approach to a small debris flow event on 19 July 2011, which was captured with a temporary monitoring network. The processing rapidly detects the debris flow event half an hour before its front arrives at the torrent mouth and 8 minutes before detection by the current alarm system. An analysis of continuous seismic records furthermore indicates that detectability of Illgraben debris flows of this size are unaffected by changing environmental and cultural seismic noise. We therefore propose that our method reliably detects initiation of the Illgraben debris flows and can thus form an important ingredient in the next generation of early warning schemes.

An Evaluation of the Timing Accuracy of Global and Regional Seismic Stations and Networks

2021 ◽  
Author(s):  
Yi Yang ◽  
Xiaodong Song ◽  
Adam T. Ringler
Keyword(s):  
Inner Core ◽  
Seismic Station ◽  
Temporal Changes ◽  
Time Range ◽  
Timing Accuracy ◽  
Seismic Stations ◽  
Arrival Times ◽  
Timing Errors ◽  
Repeating Earthquakes ◽  
Core Boundary

Abstract Clock accuracy is a basic parameter of any seismic station and has become increasingly important for seismology as the community seeks to refine structures and dynamic processes of the Earth. In this study, we measure the arrival time differences of moderate repeating earthquakes with magnitude 5.0–5.9 in the time range of 1991–2017 at the same seismic stations by cross-correlating their highly similar waveforms and thereby identify potential timing errors from the outliers of the measurements. The method has very high precision of about 10 ms and shows great potential to be used for routine inspection of the timing accuracy of historical and future digital seismic data. Here, we report 5131 probable cases of timing errors from 451 global and regional stations available from the Incorporated Research Institutions for Seismology Data Management Center, ranging from several tens of milliseconds to over 10 s. Clock accuracy seems to be a prevailing problem in permanent stations with long-running histories. Although most of the timing errors have already been tagged with low timing quality, there are quite a few exceptions, which call for greater attention from network operators and the seismological community. In addition, seismic studies, especially those on temporal changes of the Earth’s media from absolute arrival times, should be careful to avoid misinterpreting timing errors as temporal changes, which is indeed a problem in some previous studies of the Earth’s inner core boundary.

scholarly journals Osmotic stress and vesiculation as key mechanisms controlling bacterial sensitivity and resistance to TiO2 nanoparticles

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Christophe Pagnout ◽  
Angelina Razafitianamaharavo ◽  
Bénédicte Sohm ◽  
Céline Caillet ◽  
Audrey Beaussart ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Osmotic Stress ◽  
Inner Core ◽  
Metal Oxide Nanoparticles ◽  
Membrane Vesicles ◽  
Outer Core ◽  
Membrane Composition ◽  
Cell Turgor ◽  
Bacterial Sensitivity ◽  
Membrane Components

AbstractToxicity mechanisms of metal oxide nanoparticles towards bacteria and underlying roles of membrane composition are still debated. Herein, the response of lipopolysaccharide-truncated Escherichia coli K12 mutants to TiO2 nanoparticles (TiO2NPs, exposure in dark) is addressed at the molecular, single cell, and population levels by transcriptomics, fluorescence assays, cell nanomechanics and electrohydrodynamics. We show that outer core-free lipopolysaccharides featuring intact inner core increase cell sensitivity to TiO2NPs. TiO2NPs operate as membrane strippers, which induce osmotic stress, inactivate cell osmoregulation and initiate lipid peroxidation, which ultimately leads to genesis of membrane vesicles. In itself, truncation of lipopolysaccharide inner core triggers membrane permeabilization/depolarization, lipid peroxidation and hypervesiculation. In turn, it favors the regulation of TiO2NP-mediated changes in cell Turgor stress and leads to efficient vesicle-facilitated release of damaged membrane components. Remarkably, vesicles further act as electrostatic baits for TiO2NPs, thereby mitigating TiO2NPs toxicity. Altogether, we highlight antagonistic lipopolysaccharide-dependent bacterial responses to nanoparticles and we show that the destabilized membrane can generate unexpected resistance phenotype.

scholarly journals Flexural behavior of composite structural insulated panels with magnesium oxide board facings

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Łukasz Smakosz ◽  
Ireneusz Kreja ◽  
Zbigniew Pozorski
Keyword(s):  
Magnesium Oxide ◽  
Material Model ◽  
Expanded Polystyrene ◽  
Flexural Behavior ◽  
Joint Analysis ◽  
Model Parameters ◽  
Fe Model ◽  
Computational Results ◽  
Four Point Bending ◽  
Proposed Model

Abstract The current report is devoted to the flexural analysis of a composite structural insulated panel (CSIP) with magnesium oxide board facings and expanded polystyrene (EPS) core, that was recently introduced to the building industry. An advanced nonlinear FE model was created in the ABAQUS environment, able to simulate the CSIP’s flexural behavior in great detail. An original custom code procedure was developed, which allowed to include material bimodularity to significantly improve the accuracy of computational results and failure mode predictions. Material model parameters describing the nonlinear range were identified in a joint analysis of laboratory tests and their numerical simulations performed on CSIP beams of three different lengths subjected to three- and four-point bending. The model was validated by confronting computational results with experimental results for natural scale panels; a good correlation between the two results proved that the proposed model could effectively support the CSIP design process.

scholarly journals Fluid activity detection in geothermal areas using a single seismic station by monitoring horizontal-to-vertical spectral ratios

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kyosuke Okamoto ◽  
Hiroshi Asanuma ◽  
Hiro Nimiya
Keyword(s):  
Carbon Capture ◽  
Seismic Station ◽  
Carbon Capture And Storage ◽  
Fluid Flows ◽  
Temporal Variations ◽  
Geothermal Field ◽  
Spectral Ratios ◽  
Subsurface Structures ◽  
Geothermal Fields ◽  
Single Station

AbstractSubsurface structure survey based on horizontal-to-vertical (H/V) spectral ratios is widely conducted. The major merit of this survey is its convenience to obtain a stable result using a single station. Spatial variations of H/V spectral ratios are well-known phenomena, and it has been used to estimate the spatial fluctuation in subsurface structures. It is reasonable to anticipate temporal variations in H/V spectral ratios, especially in areas like geothermal fields, carbon capture and storage fields, etc., where rich fluid flows are expected, although there are few reports about the temporal changes. In Okuaizu Geothermal Field (OGF), Japan, dense seismic monitoring was deployed in 2015, and continuous monitoring has been consistent. We observed the H/V spectral ratios in OGF and found their repeated temporary drops. These drops seemed to be derived from local fluid activities according to a numerical calculation. Based on this finding, we examined a coherency between the H/V spectral ratios and fluid activities in OGF and found a significance. In conclusion, monitoring H/V spectral ratios can enable us to grasp fluid activities that sometimes could lead to a relatively large seismic event.

Exotic collagen gradients in the byssus of the mussel Mytilus edulis.

1995 ◽  
Vol 198 (3) ◽  
pp. 633-644 ◽  
Author(s):  
X Qin ◽  
J H Waite
Keyword(s):  
Amino Acid ◽  
Mytilus Edulis ◽  
Tandem Repeats ◽  
Inner Core ◽  
Immunogold Labelling ◽  
Outer Core ◽  
Complementary Distribution ◽  
Imino Acid ◽  
Molecular Masses ◽  
Straight Fiber

Byssal threads of the common mussel Mytilus edulis contain collagenous molecules from which two pepsin-resistant fragments have been isolated and characterized. These show a complementary distribution along the length of the thread, such that one predominates distally (Col-D) and the other proximally (Col-P). Both fragments contain three identical alpha-like chains with molecular masses of 50 kDa (Col-P) and 60 kDa (Col-D) and have typically collagenous amino acid compositions; for example, 35% glycine and almost 20% proline plus 4-trans-hydroxyproline. Hydroxylysine and 3-hydroxyproline were absent. Col-P sequences are also typical of collagen in consisting of tandem repeats of the triplet Gly-X-Y in which X and Y generally represent any amino acid. When proline occurs, it is hydroxylated to 4-trans-hydroxyproline only in the Y position. Seven instances where X is glycine have been detected in Col-P. Specific polyclonal anti-Col antibodies were used to isolate the precursors of Col-P and Col-D from the mussel foot. PreCol-P has a molecular mass of 95 kDa and contains 36% glycine but a lower imino acid content (13%). It has a complementary distribution with another precursor (preCol-D, 97 kDa) along the length of the foot. The two precursor compositions suggest resilin-like and silk-fibroin-like structures, respectively, in the noncollagenous domains of preCol-P and preCol-D. Immunogold labelling studies indicate that Col-P is associated with the coiled fibers of the inner core in the proximal portion of the thread, whereas Col-D is localized to the straight fiber bundles of the distal thread as well as to the outer core of the proximal thread.

Multiple inner core reflections from a Novaya Zemlya explosion

1972 ◽  
Vol 62 (4) ◽  
pp. 1063-1071 ◽  
Author(s):  
R. D. Adams
Keyword(s):  
Lower Bound ◽  
Inner Core ◽  
Nuclear Explosion ◽  
Outer Core ◽  
Low Velocity ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
Novaya Zemlya ◽  
The Core ◽  
Velocity Channel

Abstract The phases P2KP, P3KP, and P4KP are well recorded from the Novaya Zemlya nuclear explosion of October 14, 1970, with the branch AB at distances of up to 20° beyond the theoretical end point A. This extension is attributed to diffraction around the core-mantle boundary. A slowness dT/dΔ = 4.56±0.02 sec/deg is determined for the AB branch of P4KP, in excellent agreement with recent determinations of the slowness of diffracted P. This slowness implies a velocity of 13.29±0.06 km/sec at the base of the mantle, and confirms recent suggestions of a low-velocity channel above the core-mantle boundary. There is evidence that arrivals recorded before the AB branch of P2KP may lie on two branches, with different slownesses. The ratio of amplitudes of successive orders of multiple inner core reflections gives a lower bound of about 2200 for Q in the outer core.

Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years

2021 ◽  
Author(s):  
Fabian Lindner ◽  
Joachim Wassermann
Keyword(s):  
Travel Time ◽  
Seismic Velocity ◽  
Temperature Record ◽  
Lapse Time ◽  
Resistivity Tomography ◽  
Single Station ◽  
Velocity Variations ◽  
Spatio Temporal ◽  
Velocity Changes ◽  
Permafrost Thawing

<p>Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution.</p><p>Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month.</p><p>The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.</p>

Ohmic and viscous damping of the Earth's Free Core Nutation

2021 ◽  
Author(s):  
Santiago Triana ◽  
Jeremy Rekier ◽  
Antony Trinh ◽  
Veronique Dehant ◽  
Ping Zhu
Keyword(s):  
Effective Viscosity ◽  
Inner Core ◽  
Extreme Values ◽  
Ohmic Heating ◽  
Outer Core ◽  
Viscous Damping ◽  
Asymptotic Regime ◽  
Free Core Nutation ◽  
Numerical Studies ◽  
Dissipation Processes

<p>The cause for the damping of the Earth's Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN) eigenmodes has been a matter of debate since the earliest reliable estimations from nutation observations were made available. Numerical studies are difficult given the extreme values of some of the parameters associated with the Earth's fluid outer core, where important dissipation processes can take place. We present a linear numerical model for the FCN that includes viscous dissipation and Ohmic heating. We find an asymptotic regime, appropriate for Earth's parameters, where viscous and Ohmic processes contribute equally to the total damping, with the dissipation taking place almost exclusively in the boundary layers. By matching the observed nutational damping we infer an enhanced effective viscosity matching and validating methods from previous studies. We suggest that turbulence caused by the Earth's precession can be a source for the FCN's damping. </p>

scholarly journals Torsional waves driven by convection and jets in Earth’s liquid core

2018 ◽  
Vol 216 (1) ◽  
pp. 123-129 ◽  
Author(s):  
R J Teed ◽  
C A Jones ◽  
S M Tobias
Keyword(s):  
Magnetic Field ◽  
Density Gradient ◽  
Inner Core ◽  
Liquid Core ◽  
Outer Core ◽  
Dynamo Action ◽  
Radial Magnetic Field ◽  
Torsional Waves ◽  
Plausible Mechanism ◽  
Rich Liquid

SUMMARY Turbulence and waves in Earth’s iron-rich liquid outer core are believed to be responsible for the generation of the geomagnetic field via dynamo action. When waves break upon the mantle they cause a shift in the rotation rate of Earth’s solid exterior and contribute to variations in the length-of-day on a ∼6-yr timescale. Though the outer core cannot be probed by direct observation, such torsional waves are believed to propagate along Earth’s radial magnetic field, but as yet no self-consistent mechanism for their generation has been determined. Here we provide evidence of a realistic physical excitation mechanism for torsional waves observed in numerical simulations. We find that inefficient convection above and below the solid inner core traps buoyant fluid forming a density gradient between pole and equator, similar to that observed in Earth’s atmosphere. Consequently, a shearing jet stream—a ‘thermal wind’—is formed near the inner core; evidence of such a jet has recently been found. Owing to the sharp density gradient and influence of magnetic field, convection at this location is able to operate with the turnover frequency required to generate waves. Amplified by the jet it then triggers a train of oscillations. Our results demonstrate a plausible mechanism for generating torsional waves under Earth-like conditions and thus further cement their importance for Earth’s core dynamics.

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