The Dudley earthquake of 22 September, 2002

The 4.7 ML Dudley earthquake on 22 September 2002 at 23:53 (UTC) was widely felt throughout England and Wales and was the largest earth-quake to occur onshore in the United Kingdom (UK) since the magnitude 5.1 ML Bishop's Castle earthquake in 1990. The earthquake hypocentre, determined from inversion of observed P- and S-wave travel-time data suggests a source depth of 14 km and this depth estimate is also supported by forward modelling of observed waveforms. Focal mechanisms obtained from both first motion polarites of local observations and moment tensor inversion of regional observations show left-lateral strike-slip faulting along a near vertical, near north-south striking fault plane whose orientation is in good agreement with the surface expression of the observed faults in the region. Two aftershocks were recorded within the location error ellipsoid of the mainshock. Comparison of the waveform signals revealed that the mainshock and aftershocks were nearly co-located and possibly had the same source mechanism. The observed peak ground acceleration is found to be less than that predicted using five empirical relations, which have been considered applicable in the UK. Seismic moment M0 and stress drop ẟo were measured from on-scale records where Lg arrivals were clear, and then used to give better estimates of the peak ground accelerations using a stochastic approach

Remote sensing of lakes Improved chlorophyll calibration and data processing; synthesis report

Project co-ordinator; Spectral Signatures Ltd.Available from British Library Document Supply Centre-DSC:7218.469(5) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

An analysis of P times reported in the Reviewed Event Bulletin for Chinese underground explosions

Analysis of variance is used to estimate the measurement error and path effects in the P times reported in the Reviewed Event Bulletins (REBs, produced by the provisional International Data Center, Arlington, USA) and in times we have read, for explosions at the Chinese Test Site. Path effects are those differences between traveltimes calculated from tables and the true times that result in epicentre error. The main conclusions of the study are: (1) the estimated variance of the measurement error for P times reported in the REB at large signal-to-noise ratio (SNR) is 0.04 s2, the bulk of the readings being analyst-adjusted automatic-detections, whereas for our times the variance is 0.01 s2 and (2) the standard deviation of the path effects for both sets of observations is about 0.6 s. The study shows that measurement error is about twice (∼0.2 s rather than ∼0.1 s) and path effects about half the values assumed for the REB times. However, uncertainties in the estimated epicentres are poorly described by treating path effects as a random variable with a normal distribution. Only by estimating path effects and using these to correct onset times can reliable estimates of epicentre uncertainty be obtained. There is currently an international programme to do just this. The results imply that with P times from explosions at three or four stations with good SNR (so that the measurement error is around 0.1 s) and well distributed in azimuth, then with correction for path effects the area of the 90 per cent coverage ellipse should be much less than 1000 km2—the area allowed for an on-site inspection under the Comprehensive Test Ban Treaty—and should cover the true epicentre with the given probability

Quantitative drop spectroscopy using the drop analyser: theoretical and experimental approach for microvolume applications of non-turbid solutions

The drop analyser, also termed the tensiograph, is an optical fibre-based instrument system for monitoring liquids. A comprehensive assessment of the drop analyser used as a UV–visible spectrophotometer has been undertaken employing both experimental and theoretical studies. A model of the tensiograph signal (tensiotrace) has been developed using a ray-tracing approach to accurately predict the form of the tensiotrace as an aid to drop spectroscopy. An analytical equation is derived for quantitative drop spectroscopy and the form of the equation has been experimentally tested. The equation applies to both the case of a growing drop and the situation in which the drop volume is held stationary. Measurements on both stationary and moving drops are of practical value. Modelling has been used to compute the average path length of the coupled light in the drop to give a result that compares favourably with values obtained from experimental measurements. An optimized method has been identified for quantitative drop spectroscopy measurements. Results from UV–visible studies on both pollutants in water and pharmaceuticals demonstrate the utility of this approach. Two key matters relating to the practicalities of drop spectroscopy are then discussed. Some experimental studies have been made to ascertain the practical limit in analyte concentration above which variations in transmitted light from the drop shape variations result. Here, tabulated information on a representative range of liquid types has been provided as a guide to optimized spectroscopic drop analysis. Secondly, the handling of micro-volume samples is discussed. The paper concludes with a brief evaluation of the usefulness of this drop spectroscopy approach, but specifically points to the importance of drop spectroscopy for nanoscience applications