Upper limit of heaving pressure derived by pore-water pressure measurements of partially frozen soil

Experiments were conducted to estimate heaving pressures of saturated soil partially frozen in a closed system. Temperatures at both ends of a specimen were kept constant, i.e., positive at the top and negative at the bottom. When the overburden pressure P was maintained at a constant value, the pore-water pressure P_w, which showed a certain value before freezing, decreased gradually as freezing progressed, finally attaining a specific value, whereafter the specimen ceased taking water into it. The pressure difference between P and P_w, at this stage was defined as the upper limit of heaving pressure σ_u, which evidently depended on the temperature θ_c of the cooling end, in accordance with the relation: σ_u = −11.4 θ_c (kg/cm²)

It corresponds to the modified Clausius-Clapeyron's formula, which gives the freezingpoint depression of an ice—water system, where the pressure acting on the ice differs from that on the water. This is the same as the value obtained by Radd and Oertle (1973). It is considered, however, that, when θ_c lowers, the value of θ_u reaches finally a constant value smaller than the one obtained by the above equation. Denoted by σ_{u max}, it was defined as a maximum heaving pressure. The value of σ_{u max} depended on soil type.     

A site effect study of the Adapazari basin,Turkey, from strong- and weak-motion data

Approximately 4000 people were killed due to collapse of buildings in downtown Adapazari during the 1999 Izmit, Turkey earthquake (Mw = 7.4). The downtown is located on a deep sedimentary basin, so-called Adapazari basin. We study site effects of the Adapazari basin based on strong- and weak-motion data obtained by a temporary array observation deployed in and around the Adapazari basin after the earthquake. Four moderate-size aftershocks (M4.6–M5.8) are selected in our study. We evaluate the S-wave amplifications in the basin by using the traditional spectral ratio method. The spectral ratios show that the S waves are considerably amplified in the frequency range of 0.5 to about 5 Hz at the basin sites, but are apparently de-amplified at frequencies higher than about 10 Hz. We make a quantitative interpretation of the empirical amplifications based on the S-wave velocity structures at the stiff-soil reference site as well as at the basin sites; these structures were estimated by the microtremor array measurements. Through the interpretation, we confirm that the amplifications at low frequencies are attributed to the thick sedimentary layers in the Adapazari basin and that the apparent de-amplifications at high frequencies are partly due to the reference site response. In addition to the considerable S-wave amplifications, the basin site records show long-period (about 2 sec) later phases after the S-wave arrival; these later phases are basin-transduced surface waves that are originated from the source and transmitted into the basin. The predominant period of these waves apparently depends on the earthquake magnitude. We conclude that heavy damage in downtown Adapazari during the 1999 Izmit earthquake was caused not only by strongly amplified S-waves but also by long-period basin surface waves of long duration.     

Rain from shallow convective clouds—Maritime and continental

Work done initially with Y. Ogura and later by the present author was reviewed, with special emphasis on physical concepts in a cloud model. The present paper consists of two parts: a warm rain study and a graupel cloud model. The process of continuous improvement on physical ideas taken to formulate warm rain are described in the first part of this paper. It is shown that the number concentration of cloud droplets is the most sensitive factor in determining rainfall, and that there is a critical drop size distribution for initiation of rain. The second part describes a graupel cloud model and shows that graupel formation is the mechanism most likely to lead to precipitation from continental shallow convective clouds.     

Geoarchaeological investigations at the upper Paleolithic site of Kamihoronai‐Moi,Hokkaido, Japan

In order to better understand modern human behavioral variability in Hokkaido, Japan, we consider the geoarchaeology of the Kamihoronai‐Moi site in terms of its geochronology, stratigraphy, depositional environments, and post‐depositional disturbances. A Paleolithic component is stratigraphically situated between the Eniwa‐a (15,000–17,000 ¹⁴C yr B.P.) and the Tarumae‐d (8000–9000 ¹⁴C yr B.P.) tephras. Moreover, six AMS ¹⁴C ages on charcoal from a Pleistocene‐aged hearth feature are between 14,400 and 14,800 ¹⁴C yr B.P. Quantitative examinations of patterns in artifact distributions show a low degree of vertical and horizontal displacement of chipped‐stone artifacts, suggesting that post‐depositional movement of the cultural material was insufficient to disrupt the original pattern of artifact distribution. © 2009 Wiley Periodicals, Inc.     

Identification and possible recurrence of an oversized tsunami on the Pacific coast of northern Japan

Geological evidence of severe tsunami inundation has been discovered in northern Japan. In the dune fields of Shimokita, in northernmost Tohoku, we have found two distinctive sand layers that are tsunami deposits. The run-up height of >20 m and inland inundation of at least 1.4 km are notably larger than any known historical case in Japan. The tsunami-genic earthquake that resulted in these deposits is thought to have taken place in the Kuril Forearc-Trench system nearly 700 years ago. The recurrence interval of major tsunamis originating in the Kuril subduction zone is about 400 years. Given that the most recent unusually large earthquake took place in AD 1611 (corresponding to the Keicho earthquake tsunami), the findings presented here increase the potential and hazard for an outsized tsunami striking the Pacific coast of northern Japan.     

Estimating the permeability of the Nojima Fault Zone by a hydrophone vertical seismic profiling experiment

Abstract A multi-offset hydrophone vertical seismic profiling (VSP) experiment was done in a 747 m deep borehole at Nojima Hirabayashi, Hyogo prefecture, Japan. The borehole was drilled to penetrate the Nojima Fault, which was active in the 1995 Hyogo-ken Nanbu earthquake. The purpose of the hydrophone VSP is to detect subsurface permeable fractures and permeable zones and, in the present case, to estimate the permeability of the Nojima Fault. The analysis was based on a model by which tube waves are generated when incident P-waves compress the permeable fractures (or permeable zones) intersecting the borehole and a fluid in the fracture is injected into the borehole. Permeable fractures (or permeable zones) are detected at the depths of tube wave generation, and fracture permeability is calculated from the amplitude ratio of tube wave to incident P-wave. Several generations of tube waves were detected from the VSP sections. Distinct tube waves were generated at depths of the fault zone that are characterized by altered and deformed granodiorite with a fault gouge, suggesting that permeable fractures and permeable zones exist in the fault zone. Tube wave analysis shows that the permeability of the fault gouge from 624 m to 625 m is estimated to be approximately 2 × 10⁻¹² m².     

Chemical characteristics of the Cretaceous-Tertiary boundary layer at Gubbio, Italy

Platinum metals (Pd, Ir, Pt) and Au were determined by radiochemical neutron activation analysis (RNAA) on Cretaceous-Tertiary (K---T) boundary samples collected at Gubbio, Italy. In addition, about thirty elements were determined by instrumental NAA (INAA) for both the Cretaceous and the Tertiary layer samples, as well as the boundary clay samples. Iridium and other Pt metals were observed to be similarly enriched, relative to CI-chondrite, in the boundary layers, i.e., they occur in chondritic ratios. On the other hand, correlations among the metals are not very good, suggesting that Pt metals were not incorporated into clay materials in a single phase, but rather, they behaved separately according to their own solution chemistries. In the Gubbio section, the chemical composition does not change so much across the K---T boundary layer, except for Ir (and possibly other Pt group elements) and is very similar to that of the “North American shale composite (NASC)”. Arsenic and Sb were observed not to be anomalously enriched in the Gubbio K---T boundary layers. This implies that their abundances cannot be a clue in elucidating an event which must have happened at the K---T boundary period. NASC-normalized REE abundance patterns for the boundary samples show characteristic features due to some REE precipitation out of seawater. REE abundances are not variable among the Cretaceous, the Tertiary, and the boundary samples, suggesting that conditions for precipitation and sedimentation were similar across the K---T boundary at Gubbio.     

Simulating the carbon balance of a temperate larch forest under various meteorological conditions

This editorial provides a subject index from published articles, active researchers, and published papers in the field of carbon balance and management.