Earthquake relocation in the Central Alborz region of Iran using a non-linear probabilistic method

In this study, we calculate accurate absolute locations for nearly 3,000 shallow earthquakes (≤20 km depth) that occurred from 1996 to 2010 in the Central Alborz region of northern Iran using a non-linear probabilistic relocation algorithm on a local scale. We aim to produce a consistent dataset with a realistic assessment of location errors using probabilistic hypocenter probability density functions. Our results indicate significant improvement in hypocenter locations and far less scattering than in the routine earthquake catalog. According to our results, 816 earthquakes have horizontal uncertainties in the 0.5–3.0 km range, and 981 earthquakes are relocated with focal-depth errors less than 3.0 km, even with a suboptimal network geometry. Earthquake relocated are tightly clustered in the eastern Tehran region and are mainly associated with active faults in the study area (the Mosha and Garmsar faults). Strong historical earthquakes have occurred along the Mosha and Garmsar faults, and the relocated earthquakes along these faults show clear north-dipping structures and align along east–west lineations, consistent with the predominant trend of faults within the study region. After event relocation, all seismicity lies in the upper 20 km of the crust, and no deep seismicity (>20 km depth) has been observed. In many circumstances, the seismicity at depth does not correlate with surface faulting, suggesting that the faulting at depth does not directly offset overlying sediments.     

Second order elasticity theory: An improved formulation of the Grüneisen parameter at high pressure

The second order theory of elasticity, in which terms to second order in strain are retained in calculating atomic bond length changes and elastic moduli, is extended to describe thermal vibration of a face-centred cubic crystal. Coupled with equations relating the pressure dependences of elastic constants, this yields a new formulation of the thermal Grüneisen parameter γ in terms of pressure P, incompressibility K and rigidity, μ

$\text{λ}\text{1}\text{2}\text{d}\text{K}\text{d}\text{P}\text{?}\text{1}\text{2}\text{+}\text{1}\text{9}\text{P}\text{K}\text{?}\text{1}\text{3}\text{?}\text{1}\text{9}\text{P}\text{K}\text{f}\text{1?}\text{2}\text{3}\text{P}\text{K}\text{?}\text{2}\text{3}\text{P}\text{K}\text{f}$

where f = 24 (3 K ? 2 P)/(3 K + 115 μ + 90 P). The factor f arises from bond interactions and the case f = 1, representing independent bonds (no interactions), yields the free-volume γ- Since we have shown earlier that the second order elasticity theory provides a convincing explanation of the elasticity of the inner core, we believe that the new formula is appropriate for the inner core. It is, however, inadequate to describe the lower mantle γ, in which atomic bond angle rigidity, not considered here, may be appreciable.     

Fouling of floating plastic debris under Biscayne Bay exposure conditions

Six plastic/rubber materials commonly encountered in marine debris and beach litter were studied under Biscayne Bay (Florida, USA) exposure conditions to determine the effect of fouling on buoyancy. Studies under restricted floating, and restricted submerged exposure conditions suggest that most plastic samples undergo fouling to an extent to cause the sample to be negatively buoyant in sea water. Rapid defouling of the submerged fouled samples was observed. The findings suggest that free-floating plastics at sea may, under certain conditions, undergo fouling-induced sinking followed by resurfacing as floating debris.     

Seismic interaction at separation joints of an instrumented concrete bridge

A multi-span, curved, concrete box-girder bridge has been extensively instrumented by the California Strong Motion Instrumentation Program (CSMIP) in cooperation with the California Department of Transportation (Caltrans). On 28 June 1992, the bridge was shaken by the magnitude 7–5 Landers and magnitude 6–6 Big Bear earthquakes in southern California. The epicentres of these earthquakes were 50 and 29 miles (81 and 46 km) from the bridge, respectively. All 34 strong-motion sensors installed on the bridge recorded the response to these earthquakes and provided an insightful set of data. A striking aspect of the response is the presence of intermittent sharp spikes in nearly all of the acceleration records from sensors at the deck of the bridge. Among these the highest spike was 0.8g for the Landers and 1.0g for the Big Bear earthquake. The peak ground acceleration at the bridge site was only about 0.1g for both these earthquakes. With the aid of visual examination and simple analysis it is deduced that (1) the spikes were caused by forces generated at separation joints by impacts and stretching of the cable restrainers between adjacent bridge segments; (2) the forces of impacts and cable stretching are directly proportional to the size of the spikes and can be estimated by the use of a simple formula; and (3) the spikes travelled from their source to other locations on the bridge with the velocity of a compression wave propagating through concrete.     

Location and height of intertidal bars on macrotidal ridge and runnel beaches

Previous studies devoted to the morphology and hydrodynamics of ridge and runnel beaches highlight characteristics that deviate from those initially postulated by King and Williams (Geographical Journal, 1949, vol. 113, 70–85) and King (Beaches and Coasts, 1972, Edward Arnold). Disagreements on the morphodynamics of these macrotidal beaches include the position of the ridges relative to the mean neap and spring tide levels, the variation in the height of the ridges across the intertidal profile and, most importantly, whether the ridges are formed by swash or surf zone processes. The morphological characteristics of ridge and runnel beaches from three locations with varying wave, tidal and geomorphic settings were investigated to address these disagreements. Beach profiles from each site were analysed together with water‐level data collected from neighbouring ports. It was found that the ridges occur over the entire intertidal zone. On one site (north Lincolnshire, east England), the ridges are uniformly distributed over the intertidal beach, whereas on the two other sites (Blackpool beach, northwest England, and Leffrinckoucke beach, north France) there is some indication that the ridges appear to occur at preferential locations. Most significantly, the locations of the ridge crests were found to be unrelated to the positions on the intertidal profile where the water level is stationary for the longest time. It was further found that the highest ridges generally occur just above mid‐tide level where tidal non‐stationarity is greatest. These findings argue against the hypothesis that the ridges are formed by swash processes acting at stationary tide levels. It is tentatively suggested that the ridges are the result of a combination of swash and surf zone processes acting across the intertidal zone. Elucidation of the morphodynamic roles of these two types of processes, and other processes such as strong current flows in the runnels, requires further comprehensive field measurements complemented by numerical modelling. Copyright © 2001 John Wiley & Sons, Ltd.     

Implications of model uncertainty for the mapping of hillslope‐scale soil erosion predictions

An integrated modelling approach (MIRSED) which utilizes the process‐based soil erosion model WEPP (Water Erosion Prediction Project) is presented for the assessment of hillslope‐scale soil erosion at five sites throughout England and Wales. The methodology draws upon previous uncertainty analysis of the WEPP hillslope soil erosion model by the authors to qualify model results within an uncertainty framework. A method for incorporating model uncertainty from a range of sources is discussed as a first step towards using and learning from results produced through the GLUE (Generalized Likelihood Uncertainty Estimation) technique. Results are presented and compared to available observed data, which illustrate that levels of uncertainty are significant and must be taken into account if a meaningful understanding of output from models such as WEPP is to be achieved. Furthermore, the collection of quality, observed data is underlined for two reasons: as an essential tool in the development of soil erosion modelling and also to allow further constraint of model uncertainty. Copyright © 2001 John Wiley & Sons, Ltd.     

An evaluation of hemolymph cholinesterase activities in the tropical scallop,Euvola (Pecten) ziczac,for the rapid assessment of pesticide exposure

The use of sequential measurements of hemolymph cholinesterase activities as a non-invasive biomarker of seasonal organophosphate/carbamate exposure was investigated for the tropical scallop, Euvola (Pecten) ziczac. Overall activities of both acetylcholinesterase and butyrylcholinesterase were relatively high compared to studies with bivalve tissues. Acute in vivo experiments showed inhibition of hemolymph acetylcholinesterase activity at concentrations of the organophosphate insecticide chlorpyrifos of 0.1, 1 and 10 ng l(-1). Monthly sampling of hemolymph from scallops at two sites in Bermuda over a 15 month period showed seasonal acetylcholinesterase and butyrylcholinesterase inhibition. Direct and indirect evidence suggests that this inhibition did not relate to biochemical or physiological changes associated with gonad maturation and spawning, but rather reflected diffuse contamination of the marine environment by cholinesterase inhibitors or increased bioavailability of such inhibitors at these times. Repetitive sampling of scallop hemolymph for cholinesterase activities represents a rapid, sensitive and non-invasive method for assessing seasonal, sublethal pesticide exposure in these commercially important bivalves and suggests a wider use in marine pollution monitoring.