Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmos21e..05c&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #OS21E-05
Astronomy and Astrophysics
Astrophysics
4564 Tsunamis And Storm Surges, 1206 Crustal Movements: Interplate (8155), 1243 Space Geodetic Surveys
Scientific paper
The south flank of Kilauea Volcano is one of the most actively deforming regions on the planet. GPS measurements taken there since the early 1990s show a persistent seaward migration at rates exceeding 5 cm/yr. Large earthquakes occur on Kilauea with alarming frequency. The largest in historical times, a M7.2 event in 1975, caused more than 6 m of seaward displacement in addition to 3.5 m of coastal subsidence. In the last few years, an intermediate form of south flank deformation has been observed. With slip rates of about 10 cm/day, these so-called ``silent earthquake'' are much slower than the nearly instantaneous brittle failure of normal earthquakes, but vastly faster than the creep that carries the south flank relentlessly toward the sea. Kilauea is the latest subaerial volcano in an archipelago of volcanic islands stretching back to the Kamchatka Peninsula. In just the youngest part of this chain, the modern Hawaiian islands, there are more than 70 submarine debris fields, each thought to represent an ancestral flank collapse. If these collapses occurred catastrophically, they almost certainly created tsunami large enough to inundate nearby islands and perhaps long-lived enough to threaten the entire Pacific basin. Evidence for prehistoric inundation on the Hawaiian island consists of anomalously elevated detrital coral deposits, found at several locales and interpreted as the diaspora of passing tsunami. As the youngest and most active of the subaerial Hawaiian volcanoes, it is natural to wonder if Kilauea--in particular the south flank--is the most likely place for future catastrophic collapses. Since the creation of the continuous GPS network on Kilauea in the mid-1990s, as many as four silent earthquakes have been detected. Two of these, occurring in November 2000 and July 2003, have resulted in elastic deformation fields large enough to model. The modeling shows that these events occurred on a shallow ( ˜ 5 km depth) landward dipping fault, possibly the down-dip extension of the Hilina normal fault complex. Distinctive bathymetric features offshore from the south flank are highly suggestive of a buttressing toe. Thus, the entire structure of surficial normal faults, inferred down-dip extension, and the observed bathymetric morphology, can be plausibly interpreted as a listric fault that accommodates gravity-driven block rotation. If this structure also accounts for the steady creep and occasional large earthquakes, then the current active deformation within Kilauea's south flank probably promotes stability rather than catastrophe. It is difficult to see how a rotational block can ``run away'' along a listrically curved fault that is blocked at its distal end by a buttressing toe. So, Kilauea, at least in its current stage of growth, is likely not a locus for catastrophic or even large flank collapse.
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