The stochastic estimation of satellite clock correction information in WADGPS

1 IntroductionChnventional DGPS is limited by the range overwhich the differential corrections are valid due tothe rapid decorrelation of the error sources with in-creasing distance from the reference station to user.In wide area differential GPS (WWPS) errorsources in GPS measurements are medeled sepa-rately,on the basis of a limited number of referencestaitOns, to overcome this drawback. The main er-ror sources are regarded as broadcast ephemeris er-ror,atmospheric refraction and satel…     

Distribution of Indus born mica along Gulf of Kachchh coast: Implications in understanding current dynamics

Indus is one of the major sources of sediments to the Gulf of Kachchh. Yet only its <63 micron fraction is studied in detail with regards to the offshore current dynamics. Hence here we present our study on characteristic signature of the Indus sediment load (i.e. mica minerals) in >63 micron size fraction along the coast of Gulf of Kachchh. The spatial distribution of mica minerals along the Gulf of Kachchh coast was studied which showed in general decreasing trend as we move along the northern and southern coast of the Gulf of Kachchh but, an increase in amount near the southern mouth at Okha. The study shows that the earlier proposed tidal barrier is ineffective in restricting movement of mica across the mouth of the gulf due to its characteristic transport mechanism. Also the presence of mudflats along the gulf of Kachchh coast plays a vital role as sediment receptors in the active sediment transport processes and mica minerals prove to be a promising simple tracer in studying the Indus born sediments in the region.     

Estimating coseismic deformations from near source strong motion records: methods and case studies

Digital strong-motion accelerographs have opened up the possibility of extracting ground motion characteristics at much lower frequencies than was offered by analogue instruments. High-quality digital data obtained close to the faults have tempted several efforts to retrieve permanent ground displacements after an earthquake. Such attempts have been partly successful, and somewhat subjective, the main reason being the presence of baseline offsets in the accelerometric data. We review existing methods for such applications, discuss their limitations and propose a more objective and improved scheme to make baseline adjustments and obtain permanent displacements. The proposed technique is applied to 26 digital recordings from the 29 May 2008 Ölfus Earthquake in South Iceland and 9 recordings from the 1999 Chi-Chi, Taiwan, Earthquake, and the permanent displacements obtained are compared with published results and GPS measurements from nearby stations. Our case studies show that the proposed technique, in addition to being simple and objective, is effective in making adjustments for baseline errors in accelerometric data.     

Studying the Deep Structure of Elbrus Volcano by Microseismic Sounding

This paper presents results from a study of the deep structure of the Elbrus edifice and adjacent areas using geophysical techniques. We confirmed the existence of a shallow magma chamber, derived a more accurate location of the chamber in the host rocks and its characteristic dimensions, and compared new results with known studies. More accurate estimates have been obtained for the temperature at the top of the magma chamber and new evidence is adduced concerning the deep structure of the fluid magmatic systems in the Elbrus volcanic area.     

Occurrence and characteristics of sporadic sodium layer observed by lidar at a mid-latitude location

Na lidar observations of SSL during the past 5 years at a mid-latitude location (Wuhan, China, 31°N, 114°E) are reported in this paper. From 26 SSL events detected in about 230 h of observation, an SSL occurrence rate of 1 event/9 h at our location was obtained. This result, combined with that reported by Nagasawa and Abo (Geophys. Res. Lett. 22 (1995) 263) at Tokyo, Japan, reveals that the SSL occurrence can be relatively frequent at some mid-latitude locations. The statistical analyses of main parameters for the 26 SSL events were made, and the results were compared with those previously reported. By examining the corresponding data from a nearby ionosonde, it was found that there was a fairly good correlation between SSL and Es. Of the 18 pairs of SSL and Es events checked, 15 of SSL were accompanied by Es, and 8 pairs of them were correlated within 1 h in time and within 5 km in altitude. From the analyses of observed perturbations during SSL development, the role of dynamic processes of atmosphere in the SSL formations were emphasized.     

Large-scale structure of background fields and active regions

An attempt is made to study the relations between emergence of active regions and the solar background large-scale structures on the basis of Solar Geophysical Data, including Kitt-Peak magnetograms, H filtergrams, and Ca images.The emergence of 217 active regions (a.r.s) that have appeared on the solar disk not farther than ± 60° from the central meridian is studied. The a.r.s are divided into two classes A and B according to their birth location. Class A contains a.r.s emerged far (8–10°) from the background field boundaries, and class B- those emerged near to (55°) or just at the boundaries.It was found that a.r.s of class A differ appreciably from those of class B; in particular, the dimensions and the intensity (S, I) of class B a.r.s are nearly twice as large as those of class A. For class A a.r.s some alterations of the solar large-scale structure boundaries were found in 15% of all the cases, whereas for those of class B in 60%.