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  • 04.06. Seismology  (4)
  • Sea-ice growth and decay  (2)
  • Springer  (4)
  • Cambridge University Press  (2)
  • American Institute of Physics (AIP)
  • Periodicals Archive Online (PAO)
  • 2020-2023  (6)
  • 1935-1939
  • 1
    Publication Date: 2022-02-25
    Description: Physics-based broadband ground-motion simulations are generated for the strong mainshocks that occurred in the region of the Central Ionian Islands, on 26th January 2014 in Kefalonia (Mw6.1) and 17th November 2015 in Lefkas (Mw6.5). The study area is associated with frequent strong earthquakes both in the historical and instrumental eras. During the last decades, the network of strong-motion accelerographs in the area has been densified, and thus provided an adequate number of strong ground-motion records as a means to better examine the related ground-motion characteristics. In the present study, broadband ground motions for the two case studies are simulated both at selected sites and at a dense grid of points covering the affected areas. The low-frequency part of the synthetics is computed using a discrete wavenumber finite element method by convolving Green’s functions with a kinematic slip model in the frequency domain. A stochastic finite fault model approach based on a dynamic corner frequency is considered to calculate the ground motions for the higher frequencies. The broadband synthetic time series are generated after merging the results obtained from the two separate techniques, by performing a weighted summation at intermediate frequencies. The simulated values are validated by comparison with both recorded Peak Ground Acceleration (PGA) and PeakGround Velocity (PGV) values and the estimated ones by using widely accepted Ground Motion Prediction Equations (GMPEs). Our results indicate that both the spatial distribution and the amplification pattern of the simulated ground motions, in the near-field, in terms of PGA and PGV are highly influenced by the slip heterogeneity and the maximum slip patches within the seismic source.
    Description: Published
    Description: 3505–3527
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: seismic hazard ; Strong ground motion ; near-source ground motion ; Ionian Islands ; stochastic finite-fault method ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2022-03-16
    Description: In this work, we assess ground shaking in the wider Zagreb area by computing simulated seismograms at regional distances. For the purposes of the simulations, we assemble the 3D velocity and density model and test its performance. First, we compare the low-frequency simulations obtained using deterministic method for both new 3D model and a simple 1D model. We then continue the performance test by computing the full broadband seismo- grams. To do that, we apply the hybrid technique in which the low frequency (f〈1 Hz) and high frequency (f=1–10 Hz) seismograms are obtained separately using deterministic and stochastic method, respectively, and then reconciled into a single time series. We apply this method to the MW=5.3 event and four smaller (3.0〈MW〈5.0) events that occurred in the studied region. We compare simulated data with the recorded seismograms and vali- date our results by calculating the goodness of fit score for peak ground velocity and shak- ing duration. Next, to improve the understanding of the strong ground motion in this area, we simulate seismic shaking scenarios for the 1880, MW = 6.2 earthquake. From computed low-frequency waveforms, we generate shakemaps and compare the ground-motion fea- tures of the two possible sources of this event, Kašina fault and North Medvednica fault. We conduct a preliminary study to determine which fault is a more probable source of the 1880 historic event by comparing the peak ground velocities and Arias intensity with the observed intensities.
    Description: Croatian Science Foundation under the Project No. IP-2020-02-3960 European Commission, H2020 Excel- lence Science [ChEESE (Grant No. 823844)]
    Description: Published
    Description: 167–192
    Description: 1T. Struttura della Terra
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: Numerical simulation ; 3D ground motion ; Earthquake ; Central Croatia ; Zagreb ; Seismic wave propagation ; 3D crustal model ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-12-16
    Description: A new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop alongthree major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara regionto formulate reliable seismic hazard scenarios.
    Description: Published
    Description: 29–44
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: N/A or not JCR
    Keywords: North Anatolian fault · ; Sea of Marmara ; Earthquakes ; Active fault segments ; Marine geophysics ; Seismic hazard ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
    Publication Date: 2022-10-21
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Stammerjohn, S., Maksym, T., Smith, M., Cassano, J., Guest, P., Tison, J., Delille, B., Loose, B., Sedwick, P., DePace, L., Roach, L., & Parno, J. Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign. Annals of Glaciology, 61(82), (2020): 181-195, doi:10.1017/aog.2020.31.
    Description: The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
    Description: NSF supported PIPERS award numbers: ANT-1341717 (S.F. Ackley, UTSA); ANT-1341513 (E. Maksym, WHOI); ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado); ANT-1341725 (P. Guest, NPS). P. Sedwick was supported by NSF ANT-1543483. S.F. Ackley was also supported by NASA Grant 80NSSC19M0194 to the Center for Advanced Measurements in Extreme Environments at UTSA. S. Stammerjohn was also supported by the LTER Program under NFS award number ANT-0823101 (H. Ducklow, LDEO/Columbia University). Additional support was by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Bruno Delille is a research associate of the F.R.S.-FNRS. Terra-Sar-X quicklook imagery was coordinated by Kathrin Hoeppner at DLR, and Andy Archer (with the Antarctic Support Contractor) provided selected (cloud-free) MODIS scenes and daily maps of AMSR2 sea-ice concentration.
    Keywords: Atmosphere/ice/ocean interactions ; Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-10-20
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Perovich, D. K., Maksym, T., Weissling, B., & Xie, H. Surface flooding of Antarctic summer sea ice. Annals of Glaciology, 61(82), (2020): 117-126, doi:10.1017/aog.2020.22.
    Description: The surface flooding of Antarctic sea ice in summer covers 50% or more of the sea-ice area in the major summer ice packs, the western Weddell and the Bellingshausen-Amundsen Seas. Two CRREL ice mass-balance buoys were deployed on the Amundsen Sea pack in late December 2010 from the icebreaker Oden, bridging the summer period (January–February 2011). Temperature records from thermistors embedded vertically in the snow and ice showed progressive increases in the depth of the flooded layer (up to 0.3–0.35 m) on the ice cover during January and February. While the snow depth was relatively unchanged from accumulation (〈10 cm), ice thickness decreased by up to a meter from bottom melting during this period. Contemporaneous with the high bottom melting, under-ice water temperatures up to 1°C above the freezing point were found. The high temperature arises from solar heating of the upper mixed layer which can occur when ice concentration in the local area falls and lower albedo ocean water is exposed to radiative heating. The higher proportion of snow ice found in the Amundsen Sea pack ice therefore results from both winter snowfall and summer ice bottom melt found here that can lead to extensive surface flooding.
    Description: This work was supported by the National Science Foundation grant to UTSA, ANT-0839053-Sea Ice System in Antarctic Summer (S.F. Ackley, H. Xie and B. Weissling), and to WHOI, ANT-1341513 (T. Maksym), and by the NASA Center for Advanced Measurements in Extreme Environments or NASA-CAMEE at UTSA, NASA #80NSSC19M0194 (S.F. Ackley, H. Xie, B.Weissling).
    Keywords: Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay ; Snow/ice surface processes
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-05-24
    Description: The relation between macroseismic intensity and ground shaking makes it possible to transform instrumental Ground Motion Parameters (GMPs) in macroseismic intensity and vice versa, and is therefore useful for making comparisons between estimates of seismic hazard determined in terms of GMPs and macroseismic intensity, and for other engineering and seismological applications. Empirical relationships between macroseismic intensity and different recorded GMPs for the Italian territory are presented in this paper. The coefficients are calibrated using a dataset of horizontal geometrical mean GMPs, i.e. peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration (SA) at 0.2, 0.3, 1.0 and 2.0 s from the ITalian ACcelerometric Archive (ITACA; Luzi et al. 2019), and macroseismic intensity at Mercalli-Cancani-Sieberg (MCS) scale from the database DBMI15 (Locati et al. 2019). A dataset was obtained that corresponds to 240 pairs of macroseismic intensity-GMPs from 67 Italian earthquakes in the time window 1972-2016 with moment magnitude ranging from 4.2 to 6.8 and macroseismic intensity in the range [2, 10-11]. The final dataset is developed correlating strong motion stations and macroseismic intensity observations generally within 2 km from each other, but the associations is manually validated through the expert opinion. The adopted functional form is non-linear predicting macroseismic intensity as a function of LogGMPs and vice versa by performing separate regressions. The set of empirical conversion relationships GMP-I MCS -GMP and the associated standard deviations are compared with previous models. The results of an illustrative PSHA, obtained using a new seismogenic zonation (Santulin et al. 2017), proposed as one of the inputs of the new Italian seismic hazard model (Meletti et al. 2017), are used to analyse and compare seismic hazard assessment in terms of PGA and the related seismic hazard map in terms of macroseismic intensity (MCS) obtained using the empirical relationships here proposed for the PGA.
    Description: Published
    Description: 5143–5164
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: macroseismic ; intensity ; groundmotionparameters ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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