Gravity Anomalies on the Thera Islands
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Gravimetric methods have proved very useful for the study of caldera structures.
A gravity survey on the Thera Islands was first carried out by the authors (1971) on the occasion of the 1st International Scientific Congress on the Volcano Thera held in 1969. The present paper reports the gravity anomalies on the islands, revised by a supplementary survey.
The supplementary measurements were made in 1971 by a Worden gravitymeter and reached 25 in number. The distribution of the gravity points including those of the previous survey is shown in Fig. 1. The topographic corrections at all gravity points were newly calculated for a range of 15 km from the centre of the islands. The topographies of the Thera Islands and the depths of the surrounding area were read on Chart No. 2043 on a scale of 1/50,000 and Chart No. 1663 on a scale of 1/150,000 respectively.
The Bouguer anomalies, calculated on the assumption that the crust density is 2.40 g/cc, are listed in Table 1 and their distribution is shown in Fig. 2, which does not differ so much from the previous one except that the low anomaly centering on the Kammeni islands is contoured more clearly. The residual anomaly amounts to about 10 mgal along an east-west profile. The interpretation of the gravity anomalies on Thera Islands is nearly the same as the previous paper in the framework. The detailed volcanological discussions will appear in the near future.
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| For figures and tables please refer to book | |
| Figures and tables mentioned in this paper: | |
| Fig. 1: | Gravity points on Thera Islands. |
| Fig. 2: | Distribution of Bouguer anomalies on Thera Islands (unit in mgal). The crust density is assumed as 2.40 g/cc. |
| Table 1: | Gravity values on Thera Islands. |
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| Source: | "Thera and the Aegean World I" |
| Papers presented at the Second International Scientific Congress, Santorini, Greece, August 1978 | |
| Pages: | pp. 147 - 150 |
| Written by: | - I. Yokoyama Department of Geophysics, Faculty of Science, Hokkaido University, Japan - V. Bonasia Osservatorio Vesusiano, Ercolano, Napoli, Italy |
| Book information: | |
| ©Thera and the Aegean World | |
| ISBN: | 0 9506133 0 4 |
| Published by: | Thera and the Aegean World, 105-109 Bishopsgate, London EC2M 3UQ, England |
| Editor: | C. Doumas |
| To order the book from amazon.co.uk: | http://www.amazon.co.uk/exec/obidos/ASIN/0950613304/qid=1141298899/sr=1-2/ref=sr_1_0_2/203-4397765-4475969 |