Tracing woody-organic tsunami deposits of the 2011 Tohoku-oki event in Misawa (Japan)

With a minimum of three reported waves, the 2011 Tohoku-oki tsunami’s destructive force caused massive damage along the northern Japanese Aomori coast. At Misawa the coastal control area was inundated up to 550 m inland and sandy sediment remnants can be traced to c. 350 m (c. 61–63% of the maximum inundation) from the shoreline. Linking the discovery of floatable plastic objects within a woody and organic layer to our analytical data lead to the detection of a yet undocumented woody-organic tsunami deposit first appearing on top of the sandy deposit but then reaching even further inland (approx. 69–72% of the max. inundation). By this observation our understanding of the documented part of the tsunami inundation may be improved. As a consequence, sand sheets of historic and paleo-tsunamis represent minimum estimates for the coastal inundation and underestimation may be reduced by addressing the woody and organic fraction of a tsunami’s inundation.

Invisible tsunami deposits – the Misawa example, Japan

<p>With at least three reported waves, the 2011 Tohoku-oki tsunami’s destructive force caused massive damage along the Aomori coastline in northern Japan. At Misawa the coastal area was inundated up to 550 m inland and sandy sediment remnants can be traced to c. 350 m (c. 61-63% of the maximum inundation) from the shoreline.</p><p>The discovery of a floatable plastic object within a previously inconspicuous woody and organic layer in connection to our analytical data lead to the detection of a yet undocumented ‘invisible’ tsunami deposit. This layer is first appearing on top of the sandy deposit but then reaching even further inland (approx. 69-72% of the max. inundation). Initially the organic and woody layer was not evident during early stages of the field work and this would have been unchanged without the discovery of the floatable plastic particle embedded within the deposit. That critical observation was the turning point for the interpretation of the layer’s origin and thus our understanding of processes during the Tohoku-oki tsunami at the Aomori coast near Misawa harbor. Overall, may the first recognition of this woody-organic and up to now ‘invisible’ layer lead to an improvement in the understanding of tsunami processes and their sedimentological characteristics. Further, may the knowledge obtained from these types of deposits be transferred to and improve paleo-tsunami investigations, especially in rural natural environments, as sand sheets of historic and paleo-tsunamis represent minimum estimates for the coastal inundation and potential underestimations may be reduced by addressing the ‘invisible’ fraction of a tsunami’s inundation.</p>

Numerical study of a desaturation process by air injection in sandy soil

This work aims to numerically study the desaturation process in a coarse-grained sandy deposit by means of air injection. It is well-known that the soil cyclic strength to liquefaction of a saturated, sandy deposit is positively affected by the presence of gas in the void space in either a dissolved or a free form. A numerical study is performed to investigate some of the factors affecting the desaturation advance and controlling the soil desaturation process by air injection. Among these factors are: a) soil-water characteristic curve and intrinsic permeability (hydraulic parameters), b) injection time, and c) standard approach to two injection wells placement. Only the standard mechanisms of biphasic flow are investigated (i.e., incompressible and isothermal biphasic flow in an isotropic homogeneous porous media with capillary effects).

Modeling the process of hydromechanical amber extraction

The paper represents a process of hydromechanical amber extraction modeling to obtain input data and substantiate operation parameters of mining equipment to develop the improved hydromechanical technique of amber extraction. Intensification of amber mining process is possible when sandy deposit is saturated by water and air. Moreover, mechanical impact by means of vibration is added. Amber displacement within sandy deposit is considered. The deposit is characterized by environmental resistance when influence factors act on the process of amber surfacing. Amber concentration distribution over a deposit surface involving determination of floating periods of different amber fractions in terms of different operation modes as well as computer experiment concerning the amber grades and its distribution over amber-bearing deposit involved the use of computer environment Matlab. Adequate mathematical model to solve one-dimensional boundary problems for systems of parabolic and elliptic differential equations within partial first-order derivatives on one spatial variable and time has been developed. The model describes accurately the behaviour of different amber fractions within amber-bearing deposit in terms of vibration effect as well as water and air supply.

Diagnostic clarification, new morphological data and phylogenetic placement of Amphisbaena arenaria Vanzolini, 1991 (Amphisbaenia, Amphisbaenidae)

Several decades ago, Vanzolini (1991) described Amphisbaena arenaria Vanzolini, 1991 based on a single individual (MZUSP 65817) collected at Raso da Catarina, a large flat sandy deposit at the southern bank of São Francisco River. In the same paper he described A. frontalis Vanzolini, 1991 based on specimens collected at another sandy area, at the northern bank of São Francisco River, both in Bahia state, Brazil. As conflicting values are presented throughout his paper, the diagnosis of A. arenaria still needs clarification. We here comment on these differences and re-diagnose A. arenaria including new topotypic material, providing its phylogenetic placement and a new state record.

Experimental Study for Wave-Induced Oscillatory Pore Pressures in a Sandy Seabed

In this paper, an experimental study for wave-induced pore pressures in marine sediments was reported. In the experiment, a one-dimensional facility was set up with a vertical cylinder and a 1.8 m thick sandy deposit and 0.2 m thick water above the deposit. Unlike the previous experiments [1], additional static water pressures were added on the harmonic dynamic wave pressure and more pore pressure gauges were buried in the deposit, which allowed us to simulate the case with larger water depth and better describe the distribution of pore pressure trend. A series of experiments with 3000 cycles in each test were conducted under numerous different wave and soil conditions, which allowed us to examine the influence of wave and soil parameters on the wave-induced pore pressures as well as liquefaction. The experimental results show the significant influence of liquefaction on sandy seabed in shallow water. Furthermore, some new experimental phenomenon was observed. The depth of sandy deposit was usually considered to be unchanged in theoretical calculation, while the depth of which was indeed changed periodic with wave loading, which was observed and recorded in the experiments.