On an earthquake early warning system (EEW) and its applications

It is clear that the basic countermeasure against earthquake strong motion is to reinforce buildings and other structures. Realtime earthquake disaster prevention is a countermeasure during the earthquake itself and is different from realtime seismology. An EEW, earthquake early warning system, is required to trigger realtime earthquake disaster prevention. It is important to avoid too much trust in EEW for the disaster prevention. This paper describes the concept of an EEW and gives a brief history, which eventually led to the development of the UrEDAS, the urgent earthquake detection and alarm system, the first operational P-wave early warning system. A real-world example of disaster prevention by this system is described. Finally, the role of national or public organizations in earthquake disaster prevention will be discussed, with special emphasis on the situation in Japan.     

Bulk parameterization for a vegetated surface and its application to a simulation of nocturnal drainage flow

Two simple models are presented for describing the surface energy budget above vegetated surfaces. One is the traditional single-source model that includes only one energy budget equation for the entire canopy-soil system, and the other is the double-source model that includes separate energy budget equations for the vegetation canopy and the underlying soil surface. In both models, the bulk transfer coefficients needed to solve the energy budget equations are parameterized as functions of leaf area index, leaf transfer coefficients, and soil surface roughnesses to obtain the best fit to values calculated by a standard multilayer-canopy model. The validity of these models was tested by comparing their performance with that of the multilayer-canopy model for simulation of the surface energy balance and nocturnal drainage flow above vegetation. Results show that the double-source model gives reliable estimations for all cases ranging from sparse to dense vegetation covers; the single-source model is only applicable to dense, fully-covered vegetation. It is also shown that sparse vegetation weakens nocturnal drainage flow, since it isolates the cool underlying soil surface from the atmosphere above the canopy. This phenomenon cannot be described by a traditional single-source model incorporated commonly in many atmospheric models; however, the double-source model adequately describes this process.     

Geochemical characteristics of ores and surface waters for environmental risk assessment in the Pinpet iron deposit,southern Shan State,Myanmar

Mining operations in the Pinpet Fe deposit, which is the second‐largest Fe deposit in Myanmar, are currently suspended, in part because of possible contamination of heavy metals and hazardous elements (e.g., Fe, As, Cu, Zn, and U) into the surrounding aquatic environment and associated public concern. However, a scientific investigation of the source and degree of contamination in streams near the deposit has not yet been conducted. Therefore, we quantified heavy‐metal and hazardous‐element concentrations of stream waters and sediments in stream beds, and measured the speciation and concentration of these metals in deposit Fe ores using the sequential extraction method, to better understand the influence of mining activities on the surrounding environment. Geochemical results for Nan‐tank‐pauk stream and its tributaries indicate that the chemical compositions of their waters are controlled by carbonate bedrock and that no detectable contamination has occurred as a result of mining activity or hematite and limonite ore beneficiation processes in either the wet or dry seasons. All measured heavy‐metal and hazardous‐element concentrations were below the World Health Organization standards for drinking water and the proposed national drinking water quality standards in Myanmar. Bulk chemical compositions of stream‐bed and tailings dam sediments show that As, Zn, and Cu concentrations are similar to those in uncontaminated sediments. Results of bulk mineralogical and chemical analyses of ore samples reveal that some limonite ore samples contain substantial amounts of As (up to 2 wt%). However, sequential extraction results indicate that most (>90%) of the As in these As‐rich ores is hosted in insoluble fractions (e.g., crystalline Fe hydroxides and clays). Therefore, arsenic is unlikely to be released into the aquatic environment by interacting with water during ore beneficiation processes should the mine resume operations.     

Seasonal Variations of Plankton Food Web Structure in the Coastal Water off Usujiri Southwestern Hokkaido,Japan

The planktonic food web structure in the subarctic coastal water off Usujiri south-western Hokkaido, Japan was investigated from June 1997 to June 1999, based on seasonal biomass data of pico- (<2 µm), nano- (2–10 µm), micro- (10–200 µm) and mesoplankton (>200 µm), and path analysis using the structural equation model (SEM). In spring, microphytoplankton predominated due to diatom bloom, while pico- and nanophytoplankton predominated in the other seasons, except November and December 1997. The seasonal change in size distribution of heterotrophic plankton was almost similar to that of phytoplankton, and mesozooplankton biomass was high in spring. The path analyses suggest that the main channel in the microbial food web could vary according to phytoplankton size composition, indicating not only the classical food chain (microphytoplankton - copepods) but also the indirect route (microphytoplankton - naked dinoflagellates - copepods).     

Geochemical Changes in Spring Water Associated with the 2000 Eruption of the Miyakejima Volcano, Japan

Water was sampled from eight springs and a lake in volcanic Miyakejima Island of Japan after the 2000 eruption. Major chemical and isotopic compositions of the water were analyzed. Significant increases of sulfate ion are observed in several springs where the thickness of ejecta exceeds 32 mm. A good relationship of Cl/S mole ratios between spring water and leachate of the ejecta is observed. Sulfur isotopic compositions of the spring water become close to that of leachate of the ejecta as time elapses after the eruption. Consequently the sources of the added sulfate ion in the spring water after the eruption are interpreted to be anhydrite and adhered sulfur of the ejecta.     

Strong ground motion during the largest aftershock (Mw=5.8) of the 1999 Izmit earthquake, Turkey

We present a preliminary study of strong ground motion during the largest aftershock (M_w 5.8) of the 1999 Izmit earthquake (M_w 7.4), Turkey, at 11:55 on 13 September 1999. The peak ground acceleration observed near the epicentre of this aftershock was in agreement with that predicted by standard empirical prediction equations. Its spectral source parameters of the largest aftershock are also typical for a M_w 5.8 earthquake. At greater epicentral distances, there is an order-of-magnitude in scatter in peak ground acceleration values for this aftershock, which is attributed to site effects. The presence of thick layers of low-velocity sediments caused significant amplification of S-waves in the Avcılar district of Istanbul, at frequencies of 1 Hz, explaining the observed concentration of damage there as a result of the Izmit mainshock.     

Propagation Speed of a Magnetic Flux-tube Soliton with Electric Current

We present some results of a magnetic flux-tube soliton propagating along a current loop surrounded by a weakly ionized plasma, by using a 3-D Neutral-MHD simulation code. When the velocity of mass flows outside the current loop exceeds about 0.6_A, the magnetic pulse behaves as an isolated string wave which is called a curved soliton, propagating with a velocity less than that one of exterior mass flow. The propagation speed of the magnetic flux-tube soliton is studied by changing the intensity of the electric current along the flux tube, which usually cannot be observed directly. It is found that the soliton speed decreases proportionally to the increment of the electric current, and the speed is independent of the direction of the electric current. We can estimate the current intensity inside a magnetic flux-tube soliton by observations of the soliton speed and the external plasma flow velocity. These results should be compared with recent high-resolution observations of moving magnetic features (MMFs) observed near sunspots.