Crustal structure, evolution, and volcanic unrest of the Alban Hills, Central Italy |
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| Authors: | C Chiarabba A Amato P T Delaney |
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| Institution: | (1) Istituto Nazionale di Geofisica, Via di Vigna Murata, 605, I-00143 Rome, Italy Fax: +39 6 504 1181, e-mail: chiarabba@ing750.ingrm.it, IT |
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| Abstract: | The Alban Hills, a Quaternary volcanic center lying west of the central Apennines, 15–25 km southeast of Rome, last erupted
19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka. Earthquakes of moderate intensity have been generated there
at least since the Roman age. Modern observations show that intermittent periods of swarm activity originate primarily beneath
the youngest features, the phreatomagmatic craters on the west side of the volcano. Results from seismic tomography allow
identification of a low-velocity region, perhaps still hot or partially molten, more than 6 km beneath the youngest craters
and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct. Thirty centimeters
of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted
from accumulation of magma beneath these craters. The volume of magma accumulation and the amount of maximum uplift was probably
at least 40×106 m3 and 40 cm, respectively. Comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of
uplift. The magma chamber beneath the western Alban Hills is probably responsible for much of the past 200 ka of eruptive
activity, is still receiving intermittent batches of magma, and is, therefore, continuing to generate modest levels of volcanic
unrest. Bending of overburden is the most likely cause of the persistent earthquakes, which generally have hypocenters above
the 6-km-deep top of the magma reservoir. In this view, the most recent uplift and seismicity are probably characteristic
and not precursors of more intense activity.
Received: 15 April 1997 / Accepted: 9 August 1997 |
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| Keywords: | Structure Evolution Uplift Geodetic modeling Alban Hills |
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