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Committee on the Study of the Earth's
Deep Interior (SEDI)

J.L. Le Mouël

SEDI is an IUGG Union Committee to study the Earth's deep interior. SEDI began as an idea at the IAGA Scientific Assembly in Prague, Czechoslovakia, in August 1985, when IAGA Working Group I (on Theory of Planetary Magnetic Fields and Geomagnetic Secular Variation) called for the creation of a project entitled International Study of the Earth's Core and Lower Mantle, with acronym ISECALM.

It became an official program of IAGA and IUGG in 1987, and Dr. Benton served as its first Chairman from 1987 to 1991. He was succeeded by Durk Doornbos in 1991 who was Chairman until his untimely death in 1993. The then Vice-Chairman J.L. Le Mouël took over as Chairman at the next IUGG meeting at Boulder, Colorado, he will be replaced by the Chairman elect Kurt Lambeck.

SEDI is rather informally run by a Bureau (in 1994 J.L. Le Mouël, Chairman; K. Lambeck, Vice-Chairman, and D. Loper, Secretary, who has served from the begining of SEDI), and an Executive Committee (24 members for the period 1991-1994). At the last SEDI meeting in Whistler, Canada (August 1994) H.C. Nataf was approved as the European Secretary of SEDI, charged with coordinating SEDl activities within Europe. A new set of officers and Committee members for the period 1995-1996 will be chosen at an open business meeting of SEDI to be held in Boulder 1995. To assist in this process a Nominating Committee has been formed to prepare a slate of candidates for consideration at that time. SEDI issues an annual newsletter "Deep Earth dialog" put together by the SEDI Secretary.

1) The main activity of SEDI consists in holding an International symposium every other year. These symposia are very well attended and are generally held as the major meeting where questions concerning the interior of the deep Earth are debated. In 1992 the meeting was held in Mizusawa (Japan), and in 1994 in Whistler (British Columbia, Canada).

2) SEDI also sponsors symposia related to the deep Earth in most international meetings:

20th General Assembly of IUCG in Vienna, August 1991

• Union symposium: Dynamics of the Earth's deep interior and Earth rotation,
• IASPEI symposium S10: Physical properties of the Earth's Interior, mantle to core,
• IASPEI workshop SW 12: International seismic observational period,
• IAGA symposium GAM 1.2: Geodynamo processes and boundary conditions,
• IAGA symposium GAM 1.3: Numerical modeling of planetary dynamos,
• IAGA symposium GAM 1.4: Core-waves instabilities and surface flow,

Meeting of European Union of Geosciences, Strasbourg 1993

• Symposium Structure and Dynamics of the Earth's inner and outer core,

AIRAPT Conference, Colorado Springs

• Session on the physics of the iron at high pressure,

IASPEI 27th General Assembly, Wellington, New Zealand, 1994

• Symposium S4: Deep Earth discontinuities: configuration and dynamics,
• Symposium S5: Structure and composition of the Earth's Interior and their relation to planetary evolution,
• Symposium S7: Seismic topography and mantle dynamics.

3) SEDI International has encouraged the formation of SEDI national groups, some of which are quite active.

• US CSEDI Initiative

A US SEDI activity was initiated in the summer of 1991 with an informal group discussion at the IUGG General Assembly in Vienna. Subsequently the plans for the activity were debated in a series of three workshops. The activity is now called CSEDI, for Cooperative Studies of the Earth's Deep Interior. CSEDI is a community initiative aimed at making major advances in understanding how the Earth works. The CSEDI initiative was approved at a general meeting held in 1992. CSEDI held its second annual meeting in Santa Fe (N.M) in October 1993. Several workshops were organised by CSEDI in 1994 ("Time for new Earth's model", "Geomagnetic polarity reversal and field behaviour from sea sediments", "Structure of the CMB and D region", "Planetary volatiles").

• The Japanese SEDI activities mostly take the form on a 3-year program initiated in 1990: "the central core of the Earth"; it issues an annual progress report. Since mid-1991 a number of scientific meetings have been held in Japan. Japan hosted the third International SEDI symposium in Mizusawa, 1992.
• Canadian SEDI (CANSEDI) sponsors the global geodynamic project, a proposal to monitor changes in the Earth's gravity field at periods of second and longer. CANSEDI hosted the 4th international SEDI symposium at Whistler Mountain, B.C. Canada, in August 1994.
• A Chinese SEDI Committee was established in 1992 and organised the 1st China SEDI Workshop in the summer of the same year.
• The French SEDI Committee initiated a four year CNRS program of cooperative research "Terre profonde". The program started with a summer school in 1993.

There are also SEDI activities in other countries, as in Great Britain (dynamo project)... A memorial fund was established after the tragic death of the second Chairman of SEDI, Durk Doornbos. It now stands at $22,000 and the interest on the fund has been sufficient to fund three prizes during the first year of operation.

It can truly be said that SEDI is in good health: nothing important in the development of deep Earth studies is done outside of SEDI.

It must be acknowledged that this happy state of affairs is due to the untiring labors of the first two Chairmen Ned Benton and Durk Doornbos and the devoted Secretary David Loper.

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