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Rajesh Janardanan, Shamil Maksyutov, Aki Tsuruta, Fenjuan Wang, Yogesh K. Tiwari, Vinu Valsala, Akihiko Ito, Yukio Yoshida, Johannes W. Kaiser, Greet Janssens-Maenhout, Mikhail Arshinov, Motoki Sasakawa, Yasunori Tohjima, Douglas E. J. Worthy, Edward J. Dlugokencky, Michel Ramonet, Jgor Arduini, Jost V. Lavric, Salvatore Piacentino, Paul B. Krummel, Ray L. Langenfelds, Ivan Mammarella, Tsuneo Matsunaga |
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Title |
Country-Scale Analysis of Methane Emissions with a High-Resolution Inverse Model Using GOSAT and Surface Observations |
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2020 |
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Remote Sensing |
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12 |
Issue |
3 |
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375 |
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anthropogenic GOSAT inverse model methane emission UNFCCC wetland |
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We employed a global high-resolution inverse model to optimize the CH4 emission using Greenhouse gas Observing Satellite (GOSAT) and surface observation data for a period from 2011–2017 for the two main source categories of anthropogenic and natural emissions. We used the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) for anthropogenic methane emission and scaled them by country to match the national inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Wetland and soil sink prior fluxes were simulated using the Vegetation Integrative Simulator of Trace gases (VISIT) model. Biomass burning prior fluxes were provided by the Global Fire Assimilation System (GFAS). We estimated a global total anthropogenic and natural methane emissions of 340.9 Tg CH4 yr−1 and 232.5 Tg CH4 yr−1, respectively. Country-scale analysis of the estimated anthropogenic emissions showed that all the top-emitting countries showed differences with their respective inventories to be within the uncertainty range of the inventories, confirming that the posterior anthropogenic emissions did not deviate from nationally reported values. Large countries, such as China, Russia, and the United States, had the mean estimated emission of 45.7 ± 8.6, 31.9 ± 7.8, and 29.8 ± 7.8 Tg CH4 yr−1, respectively. For natural wetland emissions, we estimated large emissions for Brazil (39.8 ± 12.4 Tg CH4 yr−1), the United States (25.9 ± 8.3 Tg CH4 yr−1), Russia (13.2 ± 9.3 Tg CH4 yr−1), India (12.3 ± 6.4 Tg CH4 yr−1), and Canada (12.2 ± 5.1 Tg CH4 yr−1). In both emission categories, the major emitting countries all had the model corrections to emissions within the uncertainty range of inventories. The advantages of the approach used in this study were: (1) use of high-resolution transport, useful for simulations near emission hotspots, (2) prior anthropogenic emissions adjusted to the UNFCCC reports, (3) combining surface and satellite observations, which improves the estimation of both natural and anthropogenic methane emissions over spatial scale of countries. |
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yes |
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7660 |
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Roman Sulzbach, Hartmut Wziontek, Michael Hart-Davis, Henryk Dobslaw, Hans-Georg Scherneck, Michel Van Camp, Ove Christian Dahl Omang, Ezequiel D. Antokoletz, Christian Voigt, Denise Dettmering, Maik Thomas |
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Title |
Modeling gravimetric signatures of third-degree ocean tides and their detection in superconducting gravimeter records |
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Year |
2022 |
Publication |
Journal of Geodesy |
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Volume |
96 |
Issue |
5 |
Pages |
35 |
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Keywords |
Degree-3 tides Superconducting gravimetry Tidal analysis Tidal modeling Tide gauge data |
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Abstract |
We employ the barotropic, data-unconstrained ocean tide model TiME to derive an atlas for degree-3 tidal constituents including monthly to terdiurnal tidal species. The model is optimized with respect to the tide gauge data set TICON-td that is extended to include the respective tidal constituents of diurnal and higher frequencies. The tide gauge validation shows a root-mean-square (RMS) deviation of 0.9–1.3 mm for the individual species. We further model the load tide-induced gravimetric signals by two means (1) a global load Love number approach and (2) evaluating Greens-integrals at 16 selected locations of superconducting gravimeters. The RMS deviation between the amplitudes derived using both methods is below $$0.5 \ $$nGal ($$1 \ $$nGal $$= 0.01 \frac{\text {nm}}{\text {s}^2}$$) when excluding near-coastal gravimeters. Utilizing ETERNA-x, a recently upgraded and reworked tidal analysis software, we additionally derive degree-3 gravimetric tidal constituents for these stations, based on a hypothesis-free wave grouping approach. We demonstrate that this analysis is feasible, yielding amplitude predictions of only a few 10 nGal, and that it agrees with the modeled constituents on a level of 63–80% of the mean signal amplitude. Larger deviations are only found for lowest amplitude signals, near-coastal stations, or shorter and noisier data sets. |
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1432-1394 |
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yes |
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8578 |
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Author |
Bruhwiler L M P, Michalak A M, Tans P P |
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Title |
Spatial and temporal resolution of carbon flux estimates for 1983–2002
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Journal Article |
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Year |
2011 |
Publication |
Biogeosciences |
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Volume |
8 |
Issue |
5 |
Pages |
1309-1331 |
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Abstract |
We discuss the spatial and temporal resolution of monthly carbon flux estimates for the period 1983–2002 using a fixed-lag Kalman Smoother technique with a global chemical transport model, and the GLOBALVIEW data product. The observational network has expanded substantially over this period, and the flux estimates are better constrained provided by observations for the 1990's in comparison to the 1980's. The estimated uncertainties also decrease as observational coverage expands. In this study, we use the Globalview data product for a network that changes every 5 yr, rather than using a small number of continually-operating sites (fewer observational constraints) or a large number of sites, some of which may consist almost entirely of extrapolated data. We show that the discontinuities resulting from network changes reflect uncertainty due to a sparse and variable network. This uncertainty effectively limits the resolution of trends in carbon fluxes, and is a potentially significant source of noise in assimilation systems that allow changes in observation distribution between assimilation time steps.
The ability of the inversion to distinguish, or resolve, carbon fluxes at various spatial scales is examined using a diagnostic known as the resolution kernel. We find that the global partition between land and ocean fluxes is well-resolved even for the very sparse network of the 1980's, although prior information makes a significant contribution to the resolution. The ability to distinguish zonal average fluxes has improved significantly since the 1980's, especially for the tropics, where the zonal ocean and land biosphere fluxes can be distinguished. Care must be taken when interpreting zonal average fluxes, however, since the lack of air samples for some regions in a zone may result in a large influence from prior flux estimates for these regions. We show that many of the TransCom 3 source regions are distinguishable throughout the period over which estimates are produced. Examples are Boreal and Temperate North America. The resolution of fluxes from Europe and Australia has greatly improved since the 1990's. Other regions, notably Tropical South America and the Equatorial Atlantic remain practically unresolved.
Comparisons of the average seasonal cycle of the estimated carbon fluxes with the seasonal cycle of the prior flux estimates reveals a large adjustment of the summertime uptake of carbon for Boreal Eurasia, and an earlier onset of springtime uptake for Temperate North America. In addition, significantly larger seasonal cycles are obtained for some ocean regions, such as the Northern Ocean, North Pacific, North Atlantic and Western Equatorial Pacific, regions that appear to be well-resolved by the inversion.
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416 |
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Bachelor's thesis |
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Copernicus Publications |
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1726-4189 |
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yes |
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1685 |
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Scott D. Chambers, Susanne Preunkert, Rolf Weller, Sang-Bum Hong, Ruhi S. Humphries, Laura Tositti, Hélène Angot, Michel Legrand, Alastair G. Williams, Alan D. Griffiths, Jagoda Crawford, Jack Simmons, Taejin J. Choi, Paul B. Krummel, Suzie Molloy, Zoë Loh, Ian Galbally, Stephen Wilson, Olivier Magand, Francesca Sprovieri, Nicola Pirrone, Aurélien Dommergue |
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Title |
Characterizing Atmospheric Transport Pathways to Antarctica and the Remote Southern Ocean Using Radon-222 |
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Year |
2018 |
Publication |
Frontiers in Earth Science |
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Volume |
6 |
Issue |
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Pages |
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Keywords |
Antarctica atmospheric transport MBL Mercury Ozone Radon Southern Ocean Troposphere |
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Abstract |
We discuss remote terrestrial influences on boundary layer air over the Southern Ocean and Antarctica, and the mechanisms by which they arise, using atmospheric radon observations as a proxy. Our primary motivation was to enhance the scientific community’s ability to understand and quantify the potential effects of pollution, nutrient or pollen transport from distant land masses to these remote, sparsely-instrumented regions. Seasonal radon characteristics are discussed at 6 stations (Macquarie Island, King Sejong, Neumayer, Dumont d’Urville, Jang Bogo and Dome Concordia) using 1-4 years of continuous observations. Context is provided for differences observed between these sites by Southern Ocean radon transects between 45-67S made by the Research Vessel Investigator. Synoptic transport of continental air within the marine boundary layer (MBL) dominated radon seasonal cycles in the mid-Southern Ocean site (Macquarie Island). MBL synoptic transport, tropospheric injection, and Antarctic outflow all contributed to the seasonal cycle at the sub-Antarctic site (King Sejong). Tropospheric subsidence and injection events delivered terrestrially-influenced air to the Southern Ocean MBL in the vicinity of the circumpolar trough (or “Polar Front”). Katabatic outflow events from Antarctica were observed to modify trace gas and aerosol characteristics of the MBL 100-200 km off the coast. Radon seasonal cycles at coastal Antarctic sites were dominated by a combination of local radon sources in summer and subsidence of terrestrially-influenced tropospheric air, whereas those on the Antarctic Plateau were primarily controlled by tropospheric subsidence. Separate characterization of long-term marine and katabatic flow air masses at Dumont d’Urville revealed monthly mean differences in summer of up to 5 ppbv in ozone and 0.3 ng m-3 in gaseous elemental mercury. These differences were largely attributed to chemical processes on the Antarctic Plateau. A comparison of our observations with some Antarctic radon simulations by global climate models over the past two decades indicated that: (i) some models overestimate synoptic transport to Antarctica in the MBL, (ii) the seasonality of the Antarctic ice sheet needs to be better represented in models, (iii) coastal Antarctic radon sources need to be taken into account, and (iv) the underestimation of radon in subsiding tropospheric air needs to be investigated. |
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1028 |
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Bachelor's thesis |
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2296-6463 |
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yes |
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Serial |
7846 |
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Author |
J. Mouginot, E. Rignot, Y. Gim, D. Kirchner, E. Le Meur |
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Title |
Low-frequency radar sounding of ice in East Antarctica and southern Greenland |
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Journal |
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Year |
2014 |
Publication |
Annals of Glaciology |
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Volume |
55 |
Issue |
67 |
Pages |
138-146 |
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Keywords |
Antarctic glaciology ground-penetrating radar radio-echo sounding remote sensing |
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Abstract |
We discuss a decameter-wavelength airborne radar sounder, the Warm Ice Sounding Explorer (WISE), that provides ice thickness in areas where radar signal penetration at higher frequencies is expected to be limited. Here we report results for three campaigns conducted in Greenland (2008, 2009, 2010) and two in Antarctica (2009, 2010). Comparisons with higher-frequency radar data indicate an accuracy of ±55 m for ice-thickness measurements in Greenland and ±25 m in Antarctica. We also estimate ice thickness of the Qassimiut lobe in southwest Greenland, where few ice-thickness measurements have been made, demonstrating that WISE penetrates in strongly scattering environments. |
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1053 |
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0260-3055, 1727-5644 |
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0260-3055, 1727-5644 |
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yes |
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6793 |
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Author |
Tocheport, A.; Rivera, L.; Chevrot, S. |
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Title |
A systematic study of source time functions and moment tensors of intermediate and deep earthquakes |
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Journal Article |
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Year |
2007 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
112 |
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Keywords |
Deep earthquakes; body waves inversion; source parameters; 7203 Seismology: Body waves; 7215 Seismology: Earthquake source observations; 7209 Seismology: Earthquake dynamics; 8120 Tectonophysics: Dynamics of lithosphere and mantle: general |
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Abstract |
We developed an inversion algorithm to determine the Source Time Function and Moment Tensor of intermediate and deep earthquakes from a set of teleseismic body wave records. The method proceeds in two stages. First, a nonlinear inversion by simulated annealing is performed to simultaneously (a) align the waveforms in time, (b) determine a common source time function, and (c) measure a collection of observed station amplitudes. The station amplitudes are then used, in a second stage, as secondary observables to invert for the moment tensors. We perform three different inversions to estimate the complete moment tensor solution, the pure deviatoric solution, and the double-couple solution. All the calculations are extremely simple and, in particular, it is not necessary to compute synthetic seismograms. The method requires well-isolated phases at different stations, which restricts its application to intermediate and deep events. The algorithm is applied to the FDSN broadband records corresponding to the period 1990–2005 of worldwide intermediate and deep seismicity (depth $\ges$100 km) of magnitude greater than 6.5. The source time functions are compared to those obtained from other studies of intermediate and deep events. The moment tensors are also systematically compared to the Harvard-CMT and USGS solutions. Both show a very good agreement with previous studies. |
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133 |
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American Geophysical Union |
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ISSN |
0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5550 |
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Author |
Yagi Yuji, Nakao Atsushi, Kasahara Amato, |
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Title |
Smooth and rapid slip near the Japan Trench during the 2011 Tohoku-oki earthquake revealed by a hybrid back-projection method
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Type |
Journal Article |
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Year |
2012 |
Publication |
Earth and Planetary Science Letters |
Abbreviated Journal |
Earth Planet. Sci. Lett. |
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Volume |
355-356 |
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Pages |
94-101 |
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Keywords |
2011 Tohoku-oki earthquake, back-projection, seismic source process, smooth and rapid slip near trench, |
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Abstract |
We developed a new back-projection method that uses teleseismic P-waveforms to integrate the direct P-phase with reflected phases from structural discontinuities near the source and used it to estimate the spatiotemporal distribution of the seismic energy release of the 2011 Tohoku-oki earthquake. We projected a normalized cross-correlation of observed waveforms with corresponding Green's functions onto the seismic source region to obtain a high-resolution image of the seismic energy release. Applying this method to teleseismic P-waveform data of the 2011 Tohoku-oki earthquake, we obtained spatiotemporal distributions of seismic energy release for two frequency bands, a low-frequency dataset and a high-frequency dataset. We showed that the energy radiated in the dip direction was strongly frequency dependent. The area of major high-frequency seismic radiation extended only downdip from the hypocenter, whereas the area of major low-frequency seismic radiation propagated both downdip and updip from the hypocenter. We detected a large release of seismic energy near the Japan Trench in the area of maximum slip, which was also the source area of the gigantic tsunami, when we used only the low-frequency dataset. The timing of this large seismic energy release corresponded to an episode of smooth and rapid slip near the Japan Trench, and reflects the strong dependence of the seismic energy distribution obtained on the frequency band of the input waveform dataset. The episode of smooth and rapid slip may have been the trigger for a release of roughly all of the accumulated elastic strain in the seismic source region of the 2011 Tohoku-oki earthquake.
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133 |
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0012-821X |
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yes |
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Serial |
4647 |
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Author |
L A Ermert, K Sager, T Nissen-Meyer, A Fichtner |
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Title |
Multifrequency inversion of global ambient seismic sources |
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Journal |
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Year |
2021 |
Publication |
Geophysical Journal International |
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Volume |
225 |
Issue |
3 |
Pages |
1616-1623 |
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Abstract |
We develop and apply a method to constrain the space- and frequency-dependent location of ambient noise sources. This is based on ambient noise cross-correlation inversion using numerical wavefield simulations, which honour 3-D crustal and mantle structure, ocean loading and finite-frequency effects. In the frequency range from 3 to 20 mHz, our results constrain the global source distribution of the Earth’s hum, averaged over the Southern Hemisphere winter season of 9 yr. During Southern Hemisphere winter, the dominant sources are largely confined to the Southern Hemisphere, the most prominent exception being the Izu-Bonin-Mariana arc, which is the most active source region between 12 and 20 mHz. Generally, strong hum sources seem to be associated with either coastlines or bathymetric highs. In contrast, deep ocean basins are devoid of hum sources. While being based on the relatively small number of STS-1 broad-band stations that have been recording continuously from 2004 to 2013, our results demonstrate the practical feasibility of a frequency-dependent noise source inversion that accounts for the complexities of 3-D wave propagation. It may thereby improve full-waveform ambient noise inversions and our understanding of the physics of noise generation. |
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133 |
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ISSN |
0956-540X |
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yes |
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Call Number |
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Serial |
7992 |
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Author |
Jiuxun Yin, Marine A. Denolle, Huajian Yao |
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Title |
Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the Mw 8.3 Illapel Earthquake, Chile |
Type |
Journal |
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Year |
2018 |
Publication |
Journal of geophysical research: solid earth |
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Volume |
123 |
Issue |
1 |
Pages |
344-367 |
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Keywords |
backprojection earthquake dynamics Illapel Earthquake radiated energy |
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Abstract |
We develop a methodology that combines compressive sensing backprojection (CS-BP) and source spectral analysis of teleseismic P waves to provide metrics relevant to earthquake dynamics of large events. We improve the CS-BP method by an autoadaptive source grid refinement as well as a reference source adjustment technique to gain better spatial and temporal resolution of the locations of the radiated bursts. We also use a two-step source spectral analysis based on (i) simple theoretical Green's functions that include depth phases and water reverberations and on (ii) empirical P wave Green's functions. Furthermore, we propose a source spectrogram methodology that provides the temporal evolution of dynamic parameters such as radiated energy and falloff rates. Bridging backprojection and spectrogram analysis provides a spatial and temporal evolution of these dynamic source parameters. We apply our technique to the recent 2015 Mw 8.3 megathrust Illapel earthquake (Chile). The results from both techniques are consistent and reveal a depth-varying seismic radiation that is also found in other megathrust earthquakes. The low-frequency content of the seismic radiation is located in the shallow part of the megathrust, propagating unilaterally from the hypocenter toward the trench while most of the high-frequency content comes from the downdip part of the fault. Interpretation of multiple rupture stages in the radiation is also supported by the temporal variations of radiated energy and falloff rates. Finally, we discuss the possible mechanisms, either from prestress, fault geometry, and/or frictional properties to explain our observables. Our methodology is an attempt to bridge kinematic observations with earthquake dynamics. |
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133 |
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ISSN |
2169-9356 |
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yes |
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Call Number |
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Serial |
7876 |
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Author |
Rémi Amiraux, Simon T. Belt, Frédéric Vaultier, Virginie Galindo, Michel Gosselin, Patricia Bonin, Jean-François Rontani |
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Title |
Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers |
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Journal |
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Year |
2017 |
Publication |
Marine Chemistry |
Abbreviated Journal |
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Volume |
194 |
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Pages |
89-99 |
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Keywords |
10-DOX-like lipoxygenase Arctic environment Bacteria EPS Ice algae isomerase Light stress Lipid biomarkers Phytoplankton Salinity stress |
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Abstract |
We determined, and compared, the abiotic stress state of algae and their attached bacterial communities following their release into the water column during the Arctic sea ice melt season using specific lipid markers that are characteristic of type II photo-oxidation processes, together with those associated with cis-trans isomerase and 10S-DOX-like lipoxygenase activity, which are indicative of salinity stress. More specifically, parent lipids and some of their oxidation products were quantified in sinking particles (from sediment traps) collected from the Beaufort Sea, Resolute Passage and the Davis Strait (Canadian Arctic) in 2009, 2012 and 2015, respectively. Our data show that salinity- and light-induced bacterial stress processes are temporally decoupled, with the former occurring at the beginning of ice melting and the latter observed during the final stages of ice melt and in subsequent open waters. The salinity-induced bacterial stress seen during the early stages of ice melting contrasts the healthy state of sea ice algae under the same hypersaline conditions. As sea ice melt progresses, brine channels become hyposaline, thus reducing the bacterial salinity stress, while ice algae become susceptible to photodegradation by singlet oxygen (1O2), despite relatively low temperatures and irradiance. However, the presence of high amounts of extracellular polymeric substances (EPS) encapsulating the algae likely prevents the diffusion of 1O2 to the attached bacteria. Photo-oxidative stress is enhanced further in open waters due to the low amounts of EPS. The lower amounts of active bacteria in the Arctic compared to temperate or tropical regions is thus attributed to the combined action of efficient salinity stress in spring and photo-oxidative stress in summer. Outcomes from this study also imply that surface sediments from the Canadian Arctic contain relatively high quantities of sea ice-derived organic matter that has undergone a strong degree of salinity-induced stress. |
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Programme |
1164 |
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ISSN |
0304-4203 |
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Approved |
yes |
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Serial |
8131 |
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