HR: 10:25h
AN: G42A-01 INVITED     [Abstracts]
TI: Evolution of Deformation Studies on Active Hawaiian Volcanoes
AU: * Decker, R
EM: lavadecker@aol.com
AF: USGS (retired), Kawaihae Village 30, Kamuela, HI 96743 United States
AU: Okamura, A
EM: atokamura@verizon.com
AF: USGS (retired), 212 Pahakulani St., Hilo, HI 96720 United States
AB: Summarizing 1600 years of observations and interpretations into a brief presentation forces some difficult choices on highlighting the following techniques that are presented chronologically: Visual Observations, 400 AD to present: Missionary William Ellis' Hawaiian Guides told him that Kilauea "had been burning from time immemorial, or, to use their own words, `mai ka po mai', from chaos till now...that in earlier ages it used to boil up, overflow its banks, and inundate the adjacent country...and on occasions they supposed Pele went by a road under ground from her house in the crater to the shore". Observations of the nearly-continuous lava lake in Kilauea Caldera from 1823 until 1924 established that its surface level fluctuated from about 700 to 1100 m above sea level in 10 up-and-down episodes. Tilt Measurements, 1914 to present: Horizontal-seismometer drift and water-tube tiltmeters show that the range of long-term, ground-surface tilt radial to Halemaumau Crater exceeds 500 microradians. Triangulation and Leveling, 1920: R. M. Wilson measured deformation changes related to major Kilauea summit subsidence in 1924. The caldera area around Halemaumau subsided concentrically as much as 4 m relative to the Volcano House benchmark, and triangulation points moved toward Halemaumau by as much as 1.6 m in the caldera area. K. Mogi in 1958 modeled Kilauea leveling data and inferred 3-4 km-deep magma reservoirs. Gravity Measurements, 1959 to present: Changes were first measured during Kilauea summit subsidence related to the lower-east-rift Kapoho eruption. Surveys made before and after the 1975 M7.2 Kalapana Earthquake show that gravity changes are not a simple proxy for elevation changes. Electronic Distance Measurements (EDM), 1964 to present: D. A. Swanson, W. A. Duffield, and R. S. Fiske use EDM for trilateration proving movement of the south flank of Kilauea toward the sea. EDM show displacements as large as 8.7 m of Kilauea's south flank toward the sea related to 1975 M7.2 Earthquake. EDM provide forecasting data on 1984 Mauna Loa eruption, and infer 3-4 km-depth to Mauna Loa magma reservoirs. Global Positioning System (GPS), 1987 to present: Demonstrates changing rate of Kilauea's south flank movement toward the sea. GPS replaces most EDM monitoring of Mauna Loa's recent inflation episode. Satellite Radar Interferometry (InSAR), 1994 to present: NASA/JPL image of Kilauea Caldera area, April to October, 1994. Dilational Strain Measurements, 2000 to present: Early USGS results will be presented at this meeting.
UR: http://www.lava.name/def.htm
DE: 8110 Continental tectonics--general (0905)
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting