Hawaii is certainly one of the best known examples of regions associated to hotspot-volcanism. The Hawaii-Emperor chain was formed by hot material ascending from the earth's deep interior. While the position of the plume conduit is approximately fixed the Pacific plate slowly passes over it, leaving behind a chain of volcanic islands.
In a previous study Li et al. (2000) investigated broadband data from station KIP (Oahu) and a temporary array (HIBSN) on the Big Island. The basic findings are an updoming area of the 660 km discontinuity SW of Big Island and a low velocity zone (LVZ) in about 140 km depth beneath the SW of Big Island.
From June 1999 to May 2001 the Dublin Institute for Advanced Studies (DIAS), the University of Hawaii, Honolulu, and the GeoForschungsZentrum (GFZ), Potsdam, operated eleven mobile seismic broadband stations on the Hawaiian islands. In addition, a semipermanent broadband station was set up on the island of Maui in June 1999 which is still operational.
- June 1999 - May 2001
- Prof. Dr. R. Kind (GFZ Potsdam)
- Prof. Dr. A.W.B. Jacob* (DIAS)
- T.A. Blake (DIAS)
- Dr. X. Li (GFZ Potsdam)
- Prof. Dr. M. Weber (GFZ Potsdam)
- I. Wölbern (Uni. Frankfurt, contact person)
- Prof. Dr. F. Duennebier (Univ. of Hawaii)
- Dr. G. Rümpker (Uni. Frankfurt
- R. Habermann (Uni. Potsdam)
* Professor Brian Jacob died in 2001 on November 5th.
- Dublin Institute for Advanced Studies (DIAS), Rep. of Ireland
- University of Hawaii, Honolulu
Methods & Equipment
- teleseismic Receiver functions
- SKS splitting
- Li, X., Kind, R., Priestley, K., Sobolev, S.V., Tilmann, F., Yuan, X., Weber, M.: Mapping the Hawaiian plume conduit with converted seismic waves, nature, 405, 938-941, 2000.
The project aims to investigate influences of the plume on the upper mantle and the lithosphere. Variations in depth of the major seismic discontinuities have been investigated:
- Moho depth ranges between 13 and 17 km showing no features related to the mantle plume but a distinct dip to NW beneath the island of Oahu.
- In the SE, beneath Maui and Big Island, a clear signal occurs from within the crust partly superposing the Moho conversion.
- A negative converted phase arrives from the lithosphere-asthenosphere boundary (LAB), which is found in a depth of approx. 80 km with a quite abrupt change to 65 km beneath Oahu.
- Beneath Big Island the LVZ in about 140 km depth could be localized more excalty. Here the LAB is slightly deflected upward.
- General delays of both P410s- and P660s-phases suggest reduced S-wave velocities in almost the entire upper mantle, whereas only a small area SW of Big Island shows a significant updoming of the '660'. This implies that the Hawaii plume originates in the lower mantle.