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Stabilization of volcanic flanks by dike intrusion: An example from Kilauea

Bulletin of Volcanology

By:
and
DOI: 10.1007/s004450050278

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Abstract

Dike propagation and dilation increases the compression of adjacent rocks. On volcanoes, especially oceanic shields, dikes are accordingly thought to be structurally destabilizing. As compression is incremented, volcanic flanks are driven outward or downslope and thus increase their susceptibility to destructive earthquakes and giant landslides. We show, however, that the 2-m-thick dike emplaced along the east rift zone of Kilauea in 1983 actually stabilized that volcano's flank. Specifically, production of flank earthquakes dropped more than twofold after 1983 as maximum downslope motion slowed to 6 cm ?? year-1 from approximately 40 cm ?? year-1 during 1980-1982. As much as 65 cm of deflationary subsidence above Kilauea's summit and upper rift zones accompanied the dike intrusion. According to recent estimates, this deflation corresponds to a reduction in magma-reservoir pressure of approximately 4 MPa, probably about as much as the driving pressure of the 1983 dike. The volume of the dike, approximately 0.10-0.15 km3, is orders of magnitude less than the estimated 200- to 250-km3 volume of Kilauea's reservoir of magma and nearby hot, mushy rock. Thus, deflation of that reservoir reduces the compressional load on the flank over a much larger area than intrusion of the dike adds to it, particularly at the dominant depth of seismicity, 8-9 km. A Coulomb block model for flank motion during intervals between major earthquakes requires the low-angle fault beneath Kilauea's flank to exhibit slip weakening, conducive to earthquake instability. Accordingly, the triggering mechanism of destructive earthquakes, several of which have struck Hawaii during the past 150 years, need not require stresses accumulated by dike intrusions.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Stabilization of volcanic flanks by dike intrusion: An example from Kilauea
Series title:
Bulletin of Volcanology
DOI:
10.1007/s004450050278
Volume
61
Issue:
6
Year Published:
1999
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of Volcanology
First page:
356
Last page:
362
Number of Pages:
7