247 research outputs found
Data Set for Sandanbata et al. (2023: GRL) entitled "Two volcanic tsunami events caused by trapdoor faulting at a submerged caldera near Curtis and Cheeseman Islands in the Kermadec Arc"
No full textDescriptions
This dataset contains supplementary materials for the manuscript under revision for Geophysical Research Letters; the preprint has been uploaded to ESS Open Archive:
Sandanbata, O., Watada, S., Satake, K., Kanamori, H., & Rivera, L. (2023). Two volcanic tsunami events caused by trapdoor faulting at a submerged caldera near Curtis and Cheeseman Islands in the Kermadec Arc. Geophysical Research Letters, 50, e2022GL101086. https://doi.org/10.1029/2022GL101086
We constructed a source model for the 2017 earthquake at Curtis caldera in the Kermadec Arc. The dislocation distributions and source geometries of this source model, presented in Figure 3, are contained in this dataset
Data Set for Sandanbata et al. (2022: JGR-Solid Earth) entitled "Sub-decadal Volcanic Tsunamis Due to Submarine Trapdoor Faulting at Sumisu Caldera in the Izu-Bonin Arc"
No full textDescriptions
This dataset contains supplementary materials for the following research article:
Sandanbata, O., Watada, S., Satake, K., Kanamori, H., Rivera, L., & Zhan, Z. (2022). Sub-decadal volcanic tsunamis due to submarine trapdoor faulting at Sumisu caldera in the Izu–Bonin Arc. Journal of Geophysical Research: Solid Earth, 127, e2022JB024213. https://doi.org/10.1029/2022JB024213
We construct earthquake source models for the 2015 earthquake at Sumisu caldera in the Izu-Bonin Arc. Four source models, presented in Figures 4a, S8a, S9a, and S14a, are contained in this dataset
Evaluation of Post-license Advanced Driver Training in Italy
No full textAbstractPost-license advanced driver training addresses different categories of road users such as: novice drivers, professional drivers, company employers and recidivists. These training courses can be carried out on-track or on the road. On-track courses allow participants to gain knowledge on driving physics and experience limits in a safe road environment. On-road courses are more focused on hazard perception and situation awareness.Although extensive research has been done in this field, knowledge of the effects of these courses on road accident risk remains unclear. Previous evaluation of on-track courses did not always show a positive effect on crash rate. For example, post-license training focused on mastery of driving skills can lead to an increase of accident risk, especially on young males.However, research identified several factors that may enhance the effectiveness of driving training. In Europe a new framework for driver education and training has been proposed based on a safe driver hierarchical model (the GADGET model) and the development of a strategy for continuous learning.According to this framework, an evaluation study of on-track post-license advanced driver training has been undertaken in Italy with the main goal of assessing the safety effects of these courses and identifying training aspects to be improved. Besides crash rate, the study aims at assessing also driver behavior, knowledge of risks, self-evaluation and training quality.This paper presents the results of the possible effects of advanced driver training on driving behavior, considering in particular the number and type of violations. For each driver, data on age, gender and driving violations history were extracted from the platform and the national violations database.Three cases were addressed through a before-after analysis with control group. Case 1 considers all drivers who attended an ADT course. Case 2 aimed at understanding the effects of the courses on a specific target group: the traffic violators. Case 3 is similar to Case 2, however the control group was selected in a way that drivers characteristics and the violation rate was similar to the violation rate of the treatment group in the before period.The significance of the differences highlighted was assessed through appropriate statistical tests (i.e. paired t-test and the Wilcoxon signed-rank test).The study showed in general a higher propensity to commit traffic violations after attending an ADT course. These results are in contrast to what expected and show the necessity to diversify the training classes according to the different needs of participants
Part I. Near-source acoustic coupling between the atmosphere and the solid earth during volcanic eruptions. Part II. Nearfield normal mode amplitude anomalies of the Landers earthquake
No full textNOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
This thesis consists of two chapters. In the first chapter the normal mode theory of a spherical Earth model is extended to include the atmosphere and the theory is applied to understand the observation of air-ground acoustic coupling during volcanic eruptions and to construct synthetic ground motions. In chapter II, the fully developed normal mode theory of 3D Earth is applied to the nearfield amplitude anomalies of the surface waves of the Landers rearthquake. Synthetic seismograms for the recently-available three dimensional seismic global Earth models are constructed using the normal mode theory and compared with observations. The horizontal scale and the location of lateral seismic velocity variations which caused the amplitude anomalies are examined in detail.
Part I:
Long-period harmonic Rayleigh waves were observed by worldwide seismographic networks during the eruption of Mt. Pinatubo in 1991. It has been suggested that these Rayleigh waves were excited, through atmospheric-solid Earth coupling, by atmospheric oscillations set off by the eruption. We investigated this problem using the Earth's normal modes computed for a spherically symmetric Earth model with the solid (elastic) Earth, ocean and atmosphere. These normal modes represent Rayleigh waves in the solid Earth, tsunamis in the ocean, and Lamb waves, internal acoustic waves and internal gravity waves in the atmosphere. Since the atmosphere has a low sound velocity channel below the thermosphere (altitude 90 km), two characteristic acoustic modes with periods of 230 and 270 s exist. The energy coupling between atmospheric acoustic waves and Rayleigh waves is efficient because of the proximity of the horizontal phase velocities of these waves. The energy distribution suggests that a low altitude volcanic eruption would excite the 230 s mode more strongly than the 270 s mode. This is consistent with the observation for the Pinatubo eruption. In contrast, the internal gravity mode has a period of 300 s. The barographic oscillation at a period of 300 s observed for the 1980 Mt. St. Helens eruption is probably this mode. However, because of its slow phase velocity, it would not couple to Rayleigh waves efficiently, and cannot be detected with seismographs.
Part II-A:
The 1992 Landers earthquake ([...]=7.3) occurred in the middle of the TERRAscope network. Long-period Rayleigh waves recorded at TERRAscope stations [...] after travelling around the Earth show large amplitude anomalies, one order of magnitude larger than spherical Earth predictions up to a period of about 600 s. The ground motions over the epicentral region at and after the arrival of R4-5 are in phase at all stations. These observations are inconsistent with the nearly vertical strike slip mechanism of the Landers earthquake. Synthetic seismograms for a rotating, elliptic and laterally heterogeneous Earth model calculated by the variational method agree well with the observed waveforms. Calculations for various 3D Earth models demonstrate that the amplitudes are very sensitive to the large scale aspherical structure in the crust and the mantle. The anomalies for modes shorter than 300 s period can be explained by lateral heterogeneity shallower than the upper mantle. Rotation of the Earth and lower mantle heterogeneity are required to explain mode amplitudes at longer periods. Current whole mantle seismic tomographic models can fully explain the observed amplitudes longer than 300 s. To assess the effect of the high order lateral heterogeneity in the mantle, more precise estimate of the crustal correction is required.
Part II-B:
We modeled the interaction of the source mechanism and the station location with large-scale lateral heterogeneity using the splitting matrix of an isolated multiplet and the 'source-receiver function' whose spherical harmonic coefficients are given by [...] where s and t are angular and azimuthal order numbers respectively. For a short period of time waveform perturbation is proportional to the integral of products of the splitting function with harmonic coefficients [...] and the 'source-receiver' function. For the Landers earthquake and TERRAscope stations source-receiver geometry, the 'source-receiver function' is dominated by the low-order components, paticularly l = 2, m = ±2 in the epicentral coordinates. This beach-ball like pattern is the same for all the near-source stations located in different quadrants of the strike-slip mechanism. The two maxima of the 'beach ball' pattern coincide with the locations of the degree 2 maxima of the splitting functions; western Pacific and east of South America. These features explain the weak dependence of the waveforms on higher order lateral heterogeneity and similarity of waveforms over the epicentral region. The location and the source mechanism of the Landers earthquake relative to the large scale lateral heterogeneity l = 2, including the variations of the cruatal structures, are responsible for the cause of amplitude anomalies near the epicenter. However, the amplitude near the epicenter of an earthquake with a thrust fault type mechanism, for example the Northridge earthquake, is explained well with a spherical Earth model.</p
Progress and application of the synthesis of trans-oceanic tsunamis
No full textAbstract Abundant high-quality distant tsunami records from the 2010 Maule (Chile) and 2011 Tohoku-Oki earthquakes have revealed two distinctive features compared to long-wave tsunami simulations. The records show that the traveltime delay of the tsunami increases with distance from the earthquakes, and the initial phase reversal of tsunamis appears and grows systematically. The conventional tsunami theory cannot explain the observed waveforms and traveltimes of distant tsunamis, leading to the need for a new theory to explain and synthesize distant tsunamis. The propagating elevated sea surface of a tsunami compresses seawater and deforms the seafloor and the solid Earth. A propagating tsunami changes the mass distribution of the Earth and results in a spatiotemporal change in gravity, thereby altering the propagating tsunami itself. Incorporating these physics, we developed a new tsunami propagation theory in which a tsunami is naturally treated as a wave in a gravitationally and elastically coupled Earth system composed of solid Earth layers and an ocean layer. Two distinct tsunami simulation techniques based on the new tsunami propagation theory were introduced and confirmed to produce nearly identical tsunami waveforms. One technique treats tsunamis as free waves within a deformable Earth system, while the other treats tsunamis as external pressure and gravitational forces acting on the surface of a deformable Earth system. With the new techniques, the waveform and traveltime differences between the observed and simulated distant tsunamis disappear. Past distant tsunamis recorded by coastal tide gauges, which were not previously studied due to the traveltime and waveform mismatch problems, have become the focus of quantitative tsunami studies analyzing waveforms. New tsunami propagation techniques have been applied to the analysis of distant tsunami waveforms from the past 19 events and have helped to unveil the slip distributions of the past large earthquakes and to determine the earthquake origin time of the trans-Pacific tsunami events recorded by tide gauges since 1854
A methodology to assess pedestrian crossing safety
No full textPurpose: The safety level of a pedestrian crossing is affected by infrastructure characteristics and vehicular and pedestrian traffic level. This paper presents a methodology that allows assessing the safety level of a pedestrian crossing, regulated or not by traffic light, in an urban area according to the features of the crossing. Methods: A hierarchical structure representing factors influencing crossing safety has been developed and the relative contributions of each factor were calculated using AHP method. A composite index for crossing safety and specific indexes for main aspects included in the assessment have been developed. Results: Main assessment aspects are: Spatial and Temporal Design, Day-time and Night-time Visibility and Accessibility. Night-time Visibility resulted to have the higher weight (about 41%). Conclusion: Developed indexes allow ranking of pedestrian crossings and assigning intervention priorities, highlighting the aspects which are to be enhanced. The methodology has been used for the evaluation of 215 pedestrian crossings in 17 European cities for the Pedestrian Crossing Assessment Project co-financed by FIA Foundation. © 2010 The Author(s)
Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption
No full textLong-period harmonic Rayleigh waves were observed on seismometers during the 1991 Mt. Pinatubo eruption in the Philippines. The amplitude spectrum of the Rayleigh waves shows two distinct peaks at periods of about 230 and 270 s. In the Earth’s atmosphere, long-wavelength standing acoustic waves are bounded in a low-sound-velocity channel between the thermosphere and the ground. The Rayleigh
waves and the fundamental and first overtone of atmospheric acoustic waves trapped in the low-sound-velocity channels have approximately the same horizontal wavelength and frequency at periods of 230 and 270 s, respectively, i.e., the atmosphere and the solid earth satisfy the condition for acoustic resonant oscillations. The standing atmospheric long-wavelength acoustic waves set off by the eruption selectively excited seismic spheroidal modes near the resonant period through acoustic resonant coupling and resulted
in harmonic Rayleigh waves. In contrast, gravity waves and Lamb waves (atmospheric boundary waves) do not couple to the ground efficiently and are not easily observed as ground disturbance on seismograms during volcanic eruptions
Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption
No full textStrategies to enhance long-term competitiveness in the telecommunications industry : lessons for NTT
No full textThesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, Engineering Systems Division, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 73-75).In the telecommunications industry, the market is highly global as well as competitive in this era of Internet and data communications. Telecommunications carriers compete with not only other telecommunications carriers providing broadband access and mobile communication but also network application and service providers, which are significant threats for telecommunications carriers. It is difficult for telecommunications carriers to control the market for two significant reasons. Firstly, due to the maturity of technology as well as customers, network services have become commoditized. Secondly, telecommunications network services are vulnerable to over-the-top services based on the Internet. This study aims to investigate how large telecommunications carriers can continue to be competitive in such an environment. This paper focuses on three kinds of strategic options that enable large high-tech companies to continue to make profits; internal R&D, growth and diversification, and M&A. In the second chapter the author focuses on IBM and Cisco, which are good examples of how large companies have evolved over time, combining these three strategies. Then, the use of the three strategies by major telecommunications carriers is investigated. Finally, in the fourth chapter, the author analyzes the future competitiveness of the NTT Group, the major telecommunications carrier in Japan, using these strategies within the next decade.by Shingo Kawai.S.M. in Engineering and Managemen
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