Anomalous geomagnetic variations and the concentration of telluric currents in south - west Queensland , Australia
نویسنده
چکیده
A pattern of geomagnetic fluctuations in central Australia shown by a magnetometer array with instruments spaced at distances of order 100 km has been investigated in detail by a follow-up study in south-west Queensland with array instruments at distances of order 20 km apart. On a regional scale the pattern is simple and two-dimensional, and is evidently correlated with the spatial distribution of highly conducting sediments in the Great Artesian Basin of eastern Australia. Numerical studies of induction in two-dimensional models of the basin structure adequately account for the magnitude and scale of the observed regional pattern of anomalous fluctuation fields. The smaller scale array disclosed details in the regional pattern for which interpretation proceeds in terms of current concentration in an equivalent current sheet. This sheet represents the integrated current flow in the upper 5 km of the crust, the maximum permissible depth of such a sheet current. The interpreted current distribution can be only partly explained by the known structure of the basin. Additional conductive structures must be present either within the basin or immediately below the basin in the basement rocks. Taking into account knowledge of a conductivity anomaly in southern Australia, it is hypothesized that a current channel may exist from north to south across the Australian continent, joining the Gulf of Carpentaria to the Southern Ocean.
منابع مشابه
Harnessing the Potential to Quantify Public Preferences for Healthcare Priorities through Citizens’ Juries
Despite progress towards greater public engagement, questions about the optimal approach to access public preferences remain unanswered. We review two increasingly popular methods for engaging the public in healthcare priority-setting and determining their preferences; the Citizens’ Jury (CJ) and Discrete Choice Experiment (DCE). We discuss the theoretical framework from which each method is de...
متن کامل"anomalous Em Signals and Changes in Resistivity at Parkfield: Collaborative Research between the Universities of California at Berkeley and Riverside and Oregon
Fluctuations of resistivity have been monitored with an array measuring natural electric currents (telluric currents) in Parkfield. This array is designed to detect short-term relative changes of resistivity of 1% over days to weeks and long-term variations of 0.1% over months to years. Fractional daily variations of the telluric coefficients are computed and then compared to the earthquake rec...
متن کاملPreseismic anomalous telluric current signals observed in Kozu-shima Island, Japan.
Monitoring of telluric current, which is practically a synonym for geoelectric potential difference, was conducted on Kozu-shima Island about 170 km south of Tokyo from May 14, 1997 to June 25, 2000. During the monitoring period, 19 anomalous telluric current changes (ATCs) were observed. Their possible correlation with nearby earthquakes was statistically examined by assuming various lead time...
متن کاملTime derivative of the horizontal geomagnetic field as an activity indicator
Geomagnetically induced currents (GICs) in technological conductor systems are a manifestation of the ground effects of space weather. Large GICs are always associated with large values of the time derivative of the geomagnetic field, and especially with its horizontal component (dH/dt). By using the IMAGE magnetometer data from northern Europe from 1982 to 2001, we show that large dH/dt’s (exc...
متن کامل