Eos,Vol. 85, No. 2 , 1 3 January 2004 members, who compiled regional subsets, such as marine heat flow data (K. Louden), data from Europe (VCermak),data from China (J.YWang and S. Huang), data from Japan (S.Uyeda),data from India (M.L.Gupta),data from South Africa ( M . J o n e s ) , d a t a from the former USSR (YB.Smirnov),data from Canada (A.M.Jessop),and data from the United States (D. Blackwell and J.Sass).The authors from various publications and national catalogues also compiled additional data, such as from Africa and Australia. All data were carefully evaluated by cross-referencing and duplicate checking, original format was slightly modified, and all data were m a d e available through the World Data Center at Boulder, Colorado on floppy discs.The compilation includes 24,776 lines of data; after closely s p a c e d boreholes were averaged into o n e site, the set comprised 20,511 data points. Since the mid-1990s, the process of adding new information to the heat flow data base has b e e n kept up to date on the Web. The present custodian of the IHFC who systemati cally reviews heat flow literature is William D.
Gosnold, presently at the Department of Geol ogy and Geological Engineering, University of North Dakota.The data base can b e viewed at the Web site: http://www.heatflow.und.edu/.
Fortieth Anniversary
and Commemorative
CD
At the 23rd General Assembly of the IUGG in Sapporo, Japan, the IHFC celebrated its 40th anniversary (Figure 2 ) . T h e celebration took place at the hotel Royton Sapporo, the venue of the IUGG Assembly, on the evening of 4 July 2003.The party started with an informal recep tion, where about 100 participants gathered in a friendly atmosphere. It was followed by short speeches, violin music, and dinner, and Seiya Uyeda was honored. Details will b e presented in a Commemorative CD-ROM that is now being prepared.This CD will document the highlights of the IHFC in the past 40 years, including photos taken and s p e e c h e s given at the 40th anniversary celebration, a complete list of IHFC officers and members, a list of publications, and the current version of the
Offshore Monitoring System Records Recent Earthquake off Japan's Northernmost Island PAGE 14 Earthquakes and associated crustal move ment provide major clues for evaluating occur rences in the Earth's crust. Seismologists have tried to monitor earthquakes using integrated measurements taken by seismometers, tiltmeters, gravimeters, and Global Positioning System (GPS) receivers. For major earthquakes on land, hypocenter locations or mechanisms of earthquakes have b e e n well analyzed using dense land data. Recently fault lubrication and
IHFC heat flow data base. Any interested per son may request a free copy of this c o m m e m orative CD-ROM by sending an e-mail containing mailing address to W H. K. Lee (
[email protected]).
detailed rupture mechanisms for the 1999 Chichi earthquake in Taiwan were studied using acquired waveforms from dense obser vations surrounding the faults that caused the earthquake. On the other hand, major subductionrelated earthquakes suffer in general from a lack of constraint especially around subduction faults. There are two major shortcomings in study ing subduction-related earthquakes. One is the a b s e n c e of monitoring facilities in the off shore area. The other is the distance from land to the real source of the earthquakes. Therefore, observation instruments must b e located offshore to record earthquake signals and associated p h e n o m e n a in near field if we are to better understand the nature of plate boundary earthquakes.
References IASPEI, Resolution on heat flow, C o m p t e s R e n d u s No. 14, pp. 7 8 - 7 9 , International Association of S e i s m o l o g y and Physics of the Earth's Interior, 1964. IUGG, International Heat Flow C o m m i t t e e Meeting, Chronicle No. 54, pp. 9 0 - 9 2 , International Union of G e o d e s y and Geophysics, 1964. Pollack H. N., S. J. Hurter, and J. R. J o h n s o n , Heat flow from the Earth's interior: Analysis of the global
data set,Rev. Geophys., 3 7 , 2 6 7 - 2 8 0 , 1 9 9 3 .
Author
Information
Vladimir Cermak, Czech A c a d e m y of S c i e n c e s , Prague, Czech Republic; and William H. K. Lee, U.S. Geological Survey Menlo Park, Calif.
The 2003 Tokachi-oki earthquake was recorded by full seismic and pressure gauge data by the Japan Marine S c i e n c e and Technology Center's (JAMSTEC) real-time cabled observa tory system, which was deployed in 1999.The system is equipped with three broadband tric o m p o n e n t seismometers and two high-preci sion pressure gauges.The sensors (Figure 1) are located on the other side of any other land seismic stations at the earthquake's focal region.The system has provided invaluable seismic and tsunami data on the earthquake. The closest seismometer, OBS1, is located above the focal region about 28.6 km from the epicenter.This is the first time that such near field data have b e e n recorded for a major M8 megathrust earthquake at a subduction zone (Figure 2 ) . The pressure gauges recorded vertical uplift of the sea floor of roughly 0.4 and 0.1 m caused by the event at the PG1 and PG2 locations, respectively The observatory system is currently
0.4 m
Fig. 1 The epicenter of the 2003 Tokachi-oki earthquake is located by the solid star. (Data courtesy of the Japan Meteorological Agency.) The locations of three seismometers, KOBI, KOB2, and KOB3, and two pressure gauges, PG1 and PG2, are shown by solid triangles. These data can be combined with those from dense networks on land funded by Japanese universities and the National Institute for Earth Science and Disaster Mitigations of Japan to monitor aftershocks. NA and PA denote, respec tively, the North American and Pacific plates.
oor - 0.1 m
Time (UTC) Fig. 2. Recorded waveform and pressure fluctuations at the KOBI and PG1/2 locations are shown. Full seismic waveforms were acquired without any saturation in amplitude at all sensors. In the left panel, acceleration waveforms are shown to 0.36 m/s in the amplitudes. Seismic waveforms show that predominant frequencies of the earthquake signals are about 5 Hz and 0.2 Hz. Pressure fluctuations show that significant static changes in sea floor depths took place due to the earthquake. The uplift of the sea floor is roughly estimated as 0.4 m and 0.1 mat the PG1 and PG2 sites, respectively. These pressure gauges recorded crustal uplift, earth quake-related oscillations, and tsunamogenic pressure fluctuations. 2
Eos,Vol. 85, No. 2,13 January 2004 running without difficulty, and the acquired seismic/tsunami data are all telemetered to nationwide communities, including the Japan Meteorological Agency The real-time data are used to monitor aftershocks and to detect possible p h e n o m e n a associated with this megathrust earthquake. Japan is o n e country that has historically suffered severe damage from offshore plate boundary earthquakes. B e c a u s e main shocks of plate boundary earthquakes in subduction
zones typically take p l a c e in the offshore area, seismic signals in near field, including permanent vertical displacement right above ruptured zones, had not b e e n recorded in the past for offshore subduction-related events until the 2003 Tokachi-oki earthquake.The data acquired by the cabled system for this event will surely b e used for further studies of fault behavior at the plate boundary and for analyses of associated tsunamogenic processes. The 2003 Tokachi-oki event has proven the
Comment on "The Predictability of the Magnetosphere and Space Weather" Although the emphasis of the Eos article by Li et al. (16 September 2 0 0 3 ) describing the predictability of the magnetosphere and space weather was not history, I would like to point out two historical errors that should b e of interest to the readers of Eos. The first is the following assertion:"That the Sun might influence the Earth's magnetic field... was first realized in 1859, when the largest mag netic storm ever recorded occurred 17 hours after a white light flare on the Sun." Seven years earlier, both Sabine [1852] and Wolf [1857] independently found that geomagnetic activity had the s a m e 11-year periodicity as the num ber of sunspots. Sabine concluded "...it is quite conceivable that affections of the gaseous envelope of the sun...may give rise to sensible magnetical effects at the surface of our planet..." [Sabine,\S52]. The s e c o n d historical error is the following statement: "A viable mechanism connecting activity on the Sun with magnetic storms on the Earth was not produced until the late 1930s, when it was realized...that if the Sun emitted charged particles in a solar flare... those particles interacting with the magnetic field of the Earth would...produce a magnetic disturbance on the ground." In 1892, the famous Irish mathematical physicist George Francis Fitzgerald proposed the corpuscular hypothe sis for the source of magnetic storms, suggesting,"a sunspot is a source from which s o m e emanation like a comet's tail is projected from the Sun...Is it possible then that matter starting from the Sun with the explosive veloci ties we know possible there, and subject to an acceleration of several times solar gravitation, could reach the Earth in a couple of days?" [Fitzgerald, 1892] (Sir Oliver Lodge followed up this idea in 1900 by suggesting "...electrons flung off the sun...in their flight past the Earth... must act as an electrical current...deflect[ing] ...magnetic needles.") Unfortunately for the progress of solar-terres trial physics, Fitzgerald published his ideas the
—TOMOKI WATANABE, HIROYUKI MATSUMOTO, HlROKO SUGIOKA, HlTOSHI MlKADA, and KlYOSHI SUYEHIRO, J a p a n Marine S c i e n c e & T e c h n o l o g y Center,Yokosuka; and RlYO OTSUKA, Marine Works J a p a n , Co. Ltd., Yokohama
References
FORUM
PAGE 15
usefulness of offshore cabled observatories for acquiring real-time earthquake monitoring data for both disaster mitigation and seismological studies.
s a m e year that Kelvin gave his Royal Society Presidential address, where he reiterated his arguments m a d e nearly 30 years earlier discounting the role of the Sun in geomagnetic disturbances. Kelvin's argument was that the solar field would b e too weak to interact with the Earth's field if it propagated through empty s p a c e and had its strength fall off as a dipole [Kelvin, 1892]. Fitzgerald's corpuscular hypoth esis for magnetic storms followed several sug gestions that particles from the Sun caused the aurora m a d e by Becquerel [1880] and Goldstein [1880] (and then later by Birkeland [1896] and Lodge [ 1 9 0 0 ] ) . In addition to Fitzgerald's hypothesis, Maunder [1904] conclu sively showed that geomagnetic activity had a 27-day periodicity, the s a m e as the apparent rotation rate of the Sun. It is interesting to note that Karl Hornier, an Austrian physicist, found the s a m e thing in 1871 and Royal Astronomer Airy confirmed this periodicity in 1872, but these observations weren't widely believed until Maunder was able to show graphically a clear 27-day periodicity. Maunder proposed that the corpuscular theory of Arrhenius [1904] (which calculated that radiation pressure could drive charged particles from the Sun) was the causal link between the Sun and geomagnetic storms. In addition to these earlier works, Birkeland [1908,1913] and Chapman [1918, 1919] expanded on these corpuscular theories to explain magnetic storms. So though Li et al. are correct that our modern understanding of the "mechanism connecting activity on the Sun with magnetic storms on the Earth" c a n be traced to the 1930s [e.g., Chapman and Ferraro, 1930],this model built upon an exten sive body of work beginning in 1892. A course Web page is currently being con structed showing the time line of solar-terres trial physics, including the development of the corpuscular theory discussed above; s e e http://measure.igpp.ucla.edu/solar-terrestrialluminaries/timeline.html.) Comments are welcome. An excellent Eos article by Cliver [1994] also discusses this era of s p a c e physics.
Airy, G., On a Supposed Periodicity in the E l e m e n t s of Terrestrial Magnetism, with a Period of 2 6 1/3 Days, Proceedings of the Royal Society of London, vol.20 (pp.308-312,1871-1872). Arrhenius, S., On the physical nature of the solar
corona, Astrophysical Journal, 20,224,1904. Becquerel, W.,Memoire sur la polarisation atmospherique et Vinfluences du magnetisme terrestre sur Vatmo sphere, Dibner, Berne, 1880. Birkeland, Kr., Archives des Sciences Physiques et Naturelles, vol. l , p . 4 9 7 , 1 8 9 6 . Birkeland, Kr.,The Norwegian Aurora Polaris Expedi
tion, 1902-1903, vol. \,On the Cause of Magnetic Storms and the Origin of Terrestrial Magnetism, first section, H.Aschehoug and Co.,Christiania, 1908. Birkeland, Kr.,The Norwegian Aurora Polaris Expedi
tion, 1902-1903, vol.\,On the Cause of Magnetic Storms and the Origin of Terrestrial Magnetism, sec ond section, H.Aschehoug and Co.,Christiania, 1913. Chapman, S.,The energy of magnetic storms,Monthly
Notices Roy.Astron. Soc,
79,70-83,1918.
Chapman, S., An outline of a theory of m a g n e t i c
storms,Proc. Roy. Soc. London, A, 9 5 , 6 1 - 8 3 , 1 9 1 9 . Chapman, S. and V A. Ferraro, A new theory of mag netic storms, Nature, 126:129,1930. Cliver, E.W, Solar activity and g e o m a g n e t i c storms: The corpuscular hypothesis,Eos,Trans.AGU, 75, 609-616,1994. Fitzgerald, G. F, Sunspots and magnetic storms, The
Electrician,30,4S,\S92. Goldstein, E.,Eine neue Form elektrischer Abstossung (A n e w kind of electrical repulsion), J. Springer, Berlin, 1880. Hornstein, K , Proceedings of the Imperial A c a d e m y of S c i e n c e s of Vienna, vol. Lxiv, 1871. Kelvin, W T , Address to the Royal Society 3 0 November
1892,/Voc. Roy. Soc. London,A,
52,302-310,1892.
Lodge, Oliver, Sun spots, magnetic storms, c o m e t tails, atmospheric electricity, and aurorae, The Elec
trician, 4 6 , 2 4 9 - 2 5 0 , 1 9 0 0 . Maunder, E . W , Greenwich, Royal Observatory the "great" magnetic storms, 1875 to 1903, a n d their
association with sun-spots, Monthly Notices of the Royal Astronomical Society, 6 4 , 2 0 5 , 1 9 0 4 . Sabine, E., On periodical laws discoverable in the m e a n effects of the larger magnetic disturbances,
Philos. Trans. R. Soc. London,
142,103,1852.
Wolf, M. R., Extract of a letter addressed to General Sabine, R.A.,Treas. and VPR.S., by M.R. Wolf, dated
Zurich, 7 March 1857, Proceedings of the Royal Society ofLondon,vo\.S ( p p . 4 1 6 - 4 1 7 , 1 8 5 6 - 1 8 5 7 ) .
—MARK B . MOLDWIN, University of California at Los Angeles
