Propagation of Obliquely Incident Tsunamis on a Slope Part II Characteristics of on-Ridge Tsunamis
8
Citation
1
Reference
10
Related Paper
Citation Trend
Abstract:
Fundamental characteristics of tsunamis propagating over an oceanic ridge are investigated analytically based on the linear shallow water wave theory. The oceanic ridge model used has a triangular shape which is formed by the combination of a constant slope and a bottom of uniform depth. Wave pattern of on-ridge tsunamis varies depending on the obliquity of incident waves. Especially, standing waves are formed when the incident wave angle to the ridge exceeds the critical angle. Then no transmitted waves exist because of the evanescent waves. The present study is applied to the 1996 Irian Jaya tsunami which propagated over the South-Honshu ridge. The characteristics of on-ridge tsunamis observed at Chichijima and Hachijojima, which are close to the South-Honshu ridge, can be partly explained by using the solution derived in the present study.Keywords:
Tsunami wave
The global distributions and structure characteristics of mid-ocean ridges were introduced in this paper,including the classification of main mid-ocean ridges based on spreading rates,basic characteristics of mid-ocean ridges such as geomorphology features,the relationship between crust thickness and spreading rate,the magma chamber beneath the mid-ocean ridge as well as the interaction between the plume and the mid-ocean ridge.The applications and some important achievements of the ocean bottom seismometer(OBS) in surveys on the mid-ocean ridges were reviewed.Moreover,the principal technical scheme in our investigation on South West Indian Ridge,which is going to be fulfilled using OBS in the next year,is also briefly introduced.
Seismometer
Ocean bottom
Seafloor Spreading
Cite
Citations (0)
Less than 10% of the global mid‐ocean ridge system has been studied in detail. To remedy this problem, a program called Ridge Interdisciplinary Global Experiments (RIDGE) is integrating observational, experimental, and theoretical studies into a decade‐long effort to understand the geological, geochemical, and biological processes responsible for creating new oceanic crust along this system of ridges on the ocean floor. RIDGE tackles many scientific fronts simultaneously—since the first field program went to sea in 1991, more than 60 field programs, experimental and laboratory investigations, and theoretical studies involving over 70 investigators have been supported.
Ocean observations
Seabed
Cite
Citations (5)
We report significant progress in mid-ocean ridge research in China since China joined the InterRidge, an interdisciplinary international science program, as an associate member following the 1st InterRidge workshop in China in October 2003. Two multi-leg expeditions were conducted on the Chinese research vessel “Dayang Yihao” in 2005 and 2007, respectively. Each expedition consists multiple 30-40 day long interdisciplinary legs to investigate ocean ridge hydrothermal vents. The 2005 expedition, which was the first around the world deep sea exploration by China, has surveyed the East Pacific Rise, Mid-Atlantic Ridge, Southwest Indian Ridge, and the Central Indian Ridge. On the other hand, the 2007 expedition has investigated the Southeast Indian Ridge, Southwest Indian Ridge, Central Indian Ridge, and the Lau Basin back-arc spreading center.
Seafloor Spreading
Cite
Citations (3)
Linear analytical solutions for bottom-trapped subinertial oscillatory flow over simple ridge topographies in a stratified (two-layer) rotating fluid are presented. Results are compared to moored current meter observations of bottom-intensified motions over the Endeavour Segment of Juan de Fuca Ridge in the northeast Pacific. The solutions reproduce many of the observed features including preferential amplification of the clockwise rotary component of velocity over the ridge and increased velocity amplification with proximity to the ridge crest. For a given internal deformation radius, the degree of current amplification increases with increased bottom slope, ridge height, and oscillation frequency. Amplification decreases with increased width of the ridge relative to the deformation radius.
Crest
Clockwise
Ridge push
Oscillation (cell signaling)
Cite
Citations (27)
Mid-Atlantic Ridge
Cite
Citations (62)
Cite
Citations (0)
Global observations of mid‐ocean ridge (MOR) bathymetry demonstrate an asymmetry in axial depth across ridge offsets that is correlated with the direction of ridge migration. Motivated by these observations, we have developed two‐dimensional numerical models of asthenospheric flow and melting beneath a migrating MOR. The modification of the flow pattern produced by ridge migration leads to an asymmetry in melt production rates on either side of the ridge. By coupling a simple parametric model of three dimensional melt focusing to our simulations, we generate predictions of axial depth differences across offsets in the MOR. These predictions are quantitatively consistent with the observed asymmetry.
Ridge push
Cite
Citations (27)
Abstract Lithospheric plates diverge at mid-ocean ridges and asthenospheric mantle material rises in response. The rising material decompresses, which can result in partial melting, potentially impacting the driving forces of the system. Yet the geometry and spatial distribution of the melt as it migrates to the ridge axis are debated. Organized melt fabrics can cause strong seismic anisotropy, which can be diagnostic of melt, although this is typically not found at ridges. We present anisotropic constraints from an array of 39 ocean-bottom seismometers deployed on 0–80 Ma lithosphere from March 2016 to March 2017 near the equatorial Mid-Atlantic Ridge (MAR). Local and SKS measurements show anisotropic fast directions away from the ridge axis, which are consistent with strain and associated fabric caused by plate motions with short delay times, δt (<1.1 s). Near the ridge axis, we find several ridge-parallel fast splitting directions, φ, with SKS δt that are much longer (1.7–3.8 s). This is best explained by ridge-parallel sub-vertical orientations of sheet-like melt pockets. This observation is much different than anisotropic patterns observed at other ridges, which typically reflect fabric related to plate motions. One possibility is that thicker sub-ridge lithosphere with steep sub-ridge topography beneath slower spreading centers focuses melt into vertical, ridge-parallel melt bands, which effectively weakens the plate. Associated buoyancy forces elevate the sub-ridge plate, providing greater potential energy and enhancing the driving forces of the plates.
Seafloor Spreading
Ridge push
Mid-Atlantic Ridge
Neutral buoyancy
Seismometer
Cite
Citations (2)
The existence of a continuous, rifted, mid-oceanic ridge in the southwestern Indian Ocean, previously predicted by us, has been confirmed by soundings taken by the research vessel Vema during the expedition now in progress.
Rift valley
Rift zone
Cite
Citations (37)
[1] Global observations of mid-ocean ridge (MOR) bathymetry demonstrate an asymmetry in axial depth across ridge offsets that is correlated with the direction of ridge migration. Motivated by these observations, we have developed two-dimensional numerical models of asthenospheric flow and melting beneath a migrating MOR. The modification of the flow pattern produced by ridge migration leads to an asymmetry in melt production rates on either side of the ridge. By coupling a simple parametric model of three dimensional melt focusing to our simulations, we generate predictions of axial depth differences across offsets in the MOR. These predictions are quantitatively consistent with the observed asymmetry.
Ridge push
Cite
Citations (0)