Static pullout resistance of anchor chains in cohesionless soil—laboratory testing

This paper investigates the static pullout resistance of anchor chains embedded into cohesionless soil. The anchor chains, which are made of steel, were buried into Jumunjin sand whose relative density was set to approximately 60%. The anchor chains were horizontally pulled out through a displacement of 70?mm in laboratory model tests. Three different embedment depths and seven different numbers of chain links were adopted. The pullout resistance of the anchor chains was found to increase with increasing embedment depth and the number of anchor chain links. The measured resistance was significantly higher than the calculated frictional resistance, implying that the passive resistance at the front of the anchor chain significantly contributes to the pullout resistance. The contribution of the passive resistance tends to decrease with increasing number of chain links.     

Benthic changes at McMurdo Station, Antarctica following local sewage treatment and regional iceberg-mediated productivity decline

McMurdo Station, the largest research station in Antarctica, ceased on-site garbage dumping in 1988 and initiated sewage treatment in 2003. In 2003-2004 its sea-ice regime was altered by the massive B-15A and C-19 iceberg groundings in the Ross Sea, approximately 100 km distant. Here we follow macrofaunal response to these changes relative to a baseline sampled since 1988. In the submarine garbage dump, surface contaminants levels have declined but associated macrofaunal recolonization is not yet evident. Although sewage-associated macrofauna were still abundant around the outfall nearly 2 yr after initiation of treatment, small changes downcurrent as far as 434 m from the outfall suggest some community recovery. Widespread community changes in 2003-2004, not seen in the decade previously, suggests that the benthos collectively responded to major changes in sea-ice regime and phytoplankton production caused by the iceberg groundings.     

Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia

Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water, and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line. This explained the most visible processes taking place during the displacement.     

The August 2, 2007, Nevelsk earthquake: Instrumental data analysis

A catalogue of aftershocks of the 2007 Nevelsk earthquake (M _w = 6.2) was prepared on the basis of the data from the local network of digital seismic stations established on the southern part of Sakhalin Island. The parameters of the aftershock hypocenters were determined using the method of the seismic wave travel time inversion. The errors in the determination of the coordinates of the seismic events were analyzed. The particularities of the spatiotemporal distribution of the aftershocks in the source zone of the earthquake were established. It was shown that a strong aftershock was a subsource earthquake with its own source zone. This explains the disagreement between the energetic characteristics and the size of the aftershock zone of the Nevelsk earthquake.     

Dynamic freshwater–saline water interaction in the coastal zone of Jeju Island, South Korea

Freshwater–saline water interactions were evaluated in a coastal region influenced by external forces including tidal fluctuations and seasonal rainfall variations. Five different coastal zones were considered on Jeju Island, South Korea, and electrical conductivity (EC) profiles from the monitoring wells were examined to identify the configuration of the freshwater–saline water interface. There appeared to be discrepancies among EC profiles measured at different points in time. To analyze the dynamic behavior of freshwater–saline water interactions, groundwater level measurements and multi-depth EC and temperature probes were used to obtain time-series data; the data showed that water level, EC and temperature were influenced by both tidal fluctuations and heavy rainfall. The effects of oceanic tide on EC and temperature differed with depth due to hydraulic properties of geologic formations. A spectral filter was used to eliminate the effects of tidal forces and provide information on the influence of heavy rainfall on water level, EC and temperature. Heavy rainfall events caused different patterns and degrees of variation in EC and temperature with depth. The time-series data of EC and temperature in the subsurface at various depths enable greater understanding of the interaction processes between fresh and saline water.     

Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater

Background  

The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu).     

Occurrence of gorgosterol in diatoms of the genus Delphineis

The presence of the C₃₀ sterol gorgosterol (22,23-methylene-23,24-dimethylcholest-5-en-3ß-ol) and its analogues in some marine and freshwater environments is generally associated with invertebrate animals or dinoflagellates since there have been no reports of them in other microalgal classes. Here we show that two unialgal cultures of different species of the marine diatom Delphineis contain gorgosterol in addition to sterols more commonly found in diatoms. Our findings suggest that some reports of gorgosterol in seawater and marine sediments may well have an origin, at least in part, from diatoms.     

Constraints from precariously balanced rocks on preferred rupture directions for large earthquakes on the southern San Andreas Fault

We have compared near-fault ground motions from TeraShake simulations of M_w7.7 earthquake scenarios on the southern San Andreas Fault with precariously balanced rock locations. The TeraShake scenarios with different directions of rupture generate radically different ground motions to the northwest of the Los Angeles Basin, primarily because of directivity effects, and thus provide constraints on the ground motion and rupture direction for the latest (1690) large event on that section of the San Andreas Fault. Due to the large directional near-field ground motions predicted by the simulations, we expect the precariously balanced rocks to be located primarily in the backward rupture direction or near the epicenter. Preliminary results favor persistent nucleation at or slightly northwest of the San Gorgonia Pass fault zone for large earthquakes on the southern San Andreas Fault.