The Local Magnitude Scale in the Korean Peninsula

A formula to determine the local magnitude (M_L) following Richters original definition was empirically derived for the Korean Peninsula. A total of 1,644 digital seismograms from 142 Korean earthquakes that occurred from 1997 to 2000 were corrected for instrument response and convolved with the nominal Wood-Anderson torsion seismograph response to be appropriate for the original definition of M_L. Then, the zero-to-peak amplitude was measured in millimeters on the synthetic Wood-Anderson seismogram. Multiple regression analysis was conducted to determine distance and station correction terms for the measured peak amplitudes. The best-fit solution for M_L yielded the following formula for the Korean Peninsula:where A() and S denote the peak amplitude on the synthetic Wood-Anderson seismogram at distance and the station correction term, respectively. Note that the second term, distance correction, was adjusted with Richters M_L, taking into consideration attenuation differences between the Korean Peninsula and southern California, where Richter originally introduced M_L. On average, the magnitudes determined in this study are nearly the same as those determined by the Korea Institute of Geoscience and Mineral Resources (KIGAM), but are larger than those of the Korea Meteorological Administration (KMA) by as much as 0.36.     

Mangrove zonation in the dry life zone of the Gulf of Fonseca, Honduras

The structural attributes and zonation patterns of mangrove forests in a dry environmental setting were evaluated in relation to gradients of soil resources, soil regulators, and hydroperiod between October 2000 and August 2001 in the Gulf of Fonseca, Honduras. Transects perpendicular to the edge of tidal channels were established at four mangrove sites, each sectioned into three mangrove zones (fringe, transition, and scrub) based upon distinct tree-height gradients. Porewater sulfide concentrations among zones were normally below levels of detection (<0.03 mM) and mean redox values ranged from 163.4±9.9 to −42.4±15.8 mv, indicating slightly reducing conditions in all zones. Mean porewater NO_x ⁻ and PO₄ ³⁻ concentrations were not significantly different among zones and ranged from 3.3±0.5 to 4.5±0.4 μM and from 0.05 ±0.02 to 0.18±0.04 μM, respectively. Soil nitrogen concentrations were 1–3 mg g⁻¹ in all zones, and mean nitrogen:phosphorus atomic ratios were <20 (range: 12.9–14.9), indicative of fertile wetland soils. Mean basal areas were significantly different among mangrove zones (fringe > transition) and were coupled with differences in height within species and zones.Avicennia germinans occupied areas with higher elevations associated with higher salinities ranging from 80 to 140 g kg⁻¹ in the dry season.Rhizophora mangle dominated lower elevations where salinities ranged from 38 to 57 g kg⁻¹ in both the dry and wet seasons. Spatial analysis on mangrove seedlings along transects confirmed that seedling distribution along the intertidal profile was statistically correlated with conspecific adults, indicating that survival and growth of seedlings in different intertidal locations are closely matched to canopy membership. The sharp transition (<100 m) in forest structure and distribution of mangrove species along the intertidal zone of subhumid coastal environments demonstrate common zonation patterns where species distribution and species-specific habitat suitability are mediated closely with tolerance to soil regulators (high soil salinity) rather than resource availability.     

Natural rock joint roughness quantification through fractal techniques

Accurate quantification of roughness is important in modeling hydro-mechanical behavior of rock joints. A highly refined variogram technique was used to investigate possible existence of anisotropy in natural rock joint roughness. Investigated natural rock joints showed randomly varying roughness anisotropy with the direction. A scale dependant fractal parameter, K _v, seems to play a prominent role than the fractal dimension, D _r1d, with respect to quantification of roughness of natural rock joints. Because the roughness varies randomly, it is impossible to predict the roughness variation of rock joint surfaces from measurements made in only two perpendicular directions on a particular sample. The parameter D _r1d × K _v seems to capture the overall roughness characteristics of natural rock joints well. The one-dimensional modified divider technique was extended to two dimensions to quantify the two-dimensional roughness of rock joints. The developed technique was validated by applying to a generated fractional Brownian surface with fractal dimension equal to 2.5. It was found that the calculated fractal parameters quantify the rock joint roughness well. A new technique is introduced to study the effect of scale on two-dimensional roughness variability and anisotropy. The roughness anisotropy and variability reduced with increasing scale.     

Effects of surfactants and electrolyte solutions on the properties of soil

Biosurfactants are frequently used in petroleum hydrocarbon and dense non-aqueous phase liquids (DNAPLs) remediation. The applicability of biosurfactant use in clayey soils requires an understanding and characterization of their interaction. Comprehensive effects of surfactants and electrolyte solutions on kaolinite clay soil were investigated for index properties, compaction, strength characteristics, hydraulic conductivities, and adsorption characteristics. Sodium dodecyl sulfate (SDS) and NaPO₃ decreased the liquid limit and plasticity index of the test soil. Maximum dry unit weights were increased and optimum moisture contents were decreased as SDS and biosurfactant were added for the compaction tests for mixtures of 30% kaolinite and 70% sand. The addition of non-ionic surfactant, biosurfactant, and CaCl₂ increased the initial elastic modulus and undrained shear strength of the kaolinite–sand mixture soils. Hydraulic conductivities were measured by fixed-wall double-ring permeameters. Results showed that the hydraulic conductivity was not significantly affected, but slightly decreased from 1×10⁻⁷ cm/s (water) to 0.3×10⁻⁷ cm/s for Triton X-100 and SDS. The adsorption characteristics of the chemicals onto kaolinite were also investigated by developing isotherm curves. SDS adsorbed onto soil particles with the strongest bonding strength of the fluids tested. Correlations among parameters were developed for surfactants, electrolyte solutions, and clayey soils.     

VUGS IN ORDINARY CHONDRITES

Large vugs occur in the ordinary chondrite, Farmington. They contain the same phases present in the body of the meteorite, either as vug wall lining or as crystals attached to linings. The morphologies of these phases indicate a history of melting and vapor deposition. These vugs are compared with vugs in the ordinary chondrites, Orvinio and Tadjera, and with published reports of vugs in Rose City and Shaw. It is concluded that although shock events may not cause heating above the liquidus for the body of the meteorite, local pockets of melting and vapor formation do occur due to inhomogenieties in the shock wave pattern. Vugs represent such pockets. Vug formation, as a consequence of shock processing, is widespread among ordinary chondrites and shows no correlation with the average temperature of shock heating, subsequent average cooling rate (as indicated by metallurgical criteria), or blackening of body color.     

DISTANCE COGNITION IN URBAN ENVIRONMENTS*

Two components of urban route structure, turns and intersections, are shown to influence the estimated traversed length of a route in both laboratory and field settings. Results indicate that an increasing number of turns and intersections lead to an increase in subjective route length, and that it is the retrieval of such structural attributes from memory, rather than the storage of route information per se, that exerts the crucial influence in distance cognition. The data suggest strategies for influencing spatial decision-making, and therefore urban movement patterns, through the manipulation of cognitive distance.     

MINERALOGY AND PETROLOGY OF THE YILMIA ENSTATITE CHONDRITE

Yilmia, a new enstatite chondrite contains moderately well defined radiating and granular chondrules. The plagioclase to enstatite ratio is appreciably higher within than outside of the two granular chondrules in our microprobe sections. Osbornite was observed within the granular chondrules, but not in the rayed chondrules or surrounding matrix Major phases include enstatite, plagioclase (Ab₈₀ An₁₆ Or₄), silica, silicon-rich kamacite and titanian troilite. Minor phases are many and varied: sinoite, silicon-rich taenite, schreibersite, graphite, osbornite, oldhamite, “normal” and zincian daubreelite, ferroan alabandite and a new FeZnMn monosulfide The new mineral (Fe_.538 Zn_.246 Mn_.159 Mg_.004 S) closely resembles albandite and could easily have been overlooked in other meteorites unless a microprobe was used. A new form of oldhamite was also found. Indarch oldhamite, analyzed for comparative purposes, consists of two similar but distinct species: Ca_.96 Mn_.005 Mg_.04 Fe_.01 S and Ca_1.000 Mn_.004 Mg_.02 Fe_.005 S. These have not been reported from other meteorites Based on its mineralogy and texture this is a type II (E6) enstatite chondrite that is transitional toward the intermediate type (E5). It is unique in its mineralogical complexity, abundance of taenite, diversity of zincian minerals and monosulfides, and restriction of osbornite to certain chondrules     

Ocean-dumping research and monitoring: Strategies and tools

Ocean-dumping studies are designed to establish critical indexes of environmental quality to assess the impacts of ocean dumping. Strategies emphasized are: 1) source function characterization including determinations of toxicities of original wastes, 2) environmental characterization, 3) waste dispersion studies in the laboratory and at sea, and 4) waste biota interaction studies, both in the short term, within a life cycle of organisms affected, and in the long term, over many life cycles. Present tools include: 1) quantitative mapping of pollutant distribution by aerial remote sensing and moored and drifting arrays, 2) realtime tracking of waste dispersion in the ocean by 20- and 200-kHz acoustic records, 3) continuous multidepth water sampling to obtain sea truth, 4) in situ bioassay devices, and 5) mathematical dispersion models, some of which are similar to atmospheric chimney plume dispersion models.