Kilauea Volcano provides hot seismic data for joint Japanese-U.S. experiment

Eos, Vol. 78, No. 10, March 11, 1997 EOS,

T R A N S A C T I O N S ,

A M E R I C A N

G E O P H Y S I C A L VOLUME 78

UNION

NUMBER 10

MARCH 11,1997 PAGES 105-116

Kilauea Volcano Provides Hot Seismic Data for Joint Japanese-U.S. Experiment PAGES 105, 111

S. R. McNutt, Y . Ida, B. A. Chouet, P. Okubo, J . Oikawa, and G. Saccorotti (Japan-U.S. Working Group on Volcano Seismology) A team of 25 researchers from the United States, Japan, and Italy joined the staff of the Hawaiian Volcano Observatory (HVO) from January 8 through February 9,1996, to make the most detailed seismic recordings on Kilauea Volcano ever. One-hundred-sixteen portable seismographs were installed in and near Kilauea Crater in Hawaii Volcanoes National Park as a joint Japanese-U.S. research project to record volcanic earthquakes and tremor. The importance of these events has long b e e n recognized, but their origin remains poorly understood due to inadequate network coverage and limitations of the analog instru­ mentation used in the past. On February 1, a swarm of over 500 earth­ quakes was recorded by the dense network, providing the best recording of an intrusive earthquake swarm at Kilauea. The data col­ lected offer an u n p r e c e d e n t e d opportunity to understand earthquakes associated with m a g m a transport. Experiment This project was begun under a JapanU.S. S c i e n c e and T e c h n o l o g y (JUST) agree­ ment for natural hazards reduction and mitigation. A JUST working group on v o l c a n o seismology selected Kilauea V o l c a n o , Ha­ waii, as a study site, s i n c e its ongoing erup­ tion provides a unique opportunity for a large-scale seismic monitoring effort. Three dense arrays of seismographs were deployed (Figure 1) to record earthquakes and tremor activity originating b e n e a t h Kilauea's summit caldera. The first array was For m o r e i n f o r m a t i o n , c o n t a c t S t e v e McNutt, A l a s k a V o l c a n o O b s e r v a t o r y , G e o p h y s i c a l Insti­ t u t e , University of A l a s k a F a i r b a n k s , 9 0 3 K u y u k u k Drive, P.O. B o x 7 5 7 3 2 0 , F a i r b a n k s , AK 9 9 7 7 5 - 7 3 2 0 .

a 300-m aperture a n t e n n a consisting of 31 three-component sensors (Figure 2 ) . T h e arc spacing of 50 m and sensor interval were se­

1996

lected to assure optimum sampling of signals for frequency-slowness studies [Goldstein and Chouet, 1994] and for investigations of the polarization and phase velocities of the wave fields using the stochastic wave method [Aki, 1957, 1965; Ferrazini et al., 1991]. Similar a n t e n n a s have b e e n deployed at other v o l c a n i c sites in the past [Dietel et al, 1 9 8 9 , 1 9 9 4 ] . The s e c o n d Kilauea array consisted of two c o n c e n t r i c rings with diameters of 2 and 4 km, respectively, surrounding a central re­ ceiver (Figure 1). This configuration pro­ vided e x c e l l e n t azimuthal c o v e r a g e for events occurring b e n e a t h Halemaumau Cra­ ter near the c e n t e r of the array. A similar ex­ periment in the near field surrounding the Izu-Oshima crater revealed that the tremor

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LONGITUDE (DEG) Fig. 1. Map of the entire January 1996 portable seismic network, including outlines of Kilauea caldera and Halemaumau crater, and positions of major faults. Each dot marks the position of a seismic station; clusters of small dots mark two dense subarrays. TheAl antenna is just to the left of the label for station C1D, and the B linear array (indicated by line) extends from station COO to the southeast through C1E. "1996 Arrays" refers to the instrument configurations in 1996.

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Eos, Vol. 78, No. 10, March 11, 1997 A1 ANTENNA

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was c o m p o s e d of the type of isotropic waves that would b e e x p e c t e d from volumetric vi­ bration at the s o u r c e [Yamaoka et al. 1991]. The third array consisted of 48 sensors along a line oriented south-southeast from the cen­ ter of the circular network (Figure 2 ) . The re­ ceiver spacing of 35 m ensured wave c o h e r e n c e b e t w e e n adjacent stations. This dense linear array was deployed to study wave transmission as a function of distance. A similar dense array was deployed at IzuOshima to determine the s o u r c e time func­ tion of volcanic tremor [Oikawa etal, 1994]. Additional receivers were added to the south­ west and northwest arms of the circular ar­ rays to improve station density. R e c e i v e r positions were determined by the Global Po­ sitioning System for the entire network. The equipment installed on Kilauea in­ cluded portable, digital data loggers that re­ c o r d e d up to three seismic data c h a n n e l s with a Global Positioning System time signal. Power was supplied by a r e c h a r g e a b l e bat­ tery. Up to 20 MB of data were recorded in the data logger flash memory and then down­ loaded into n o t e b o o k computers during site visits. Data were then downloaded from the n o t e b o o k computers into a workstation at HVO. The data loggers were run in continu­ ous m o d e from January 11 through January 21, and in event-triggered m o d e thereafter. The network of seismometers and port­ a b l e data loggers was nested within the net­ work of permanent seismic stations that transmit their signals via FM radio for record­ ing and analysis at HVO. Over the past few years, HVO has upgraded its instrumentation and data transmission and acquisition s c h e m e s , and in 1993 a network of 10 digi­ tally telemetered, three-component broad­ b a n d seismometers was installed in the summit region. With the 123 c h a n n e l s of seis­ mic data presently transmitted to HVO, the

Fig. 2. Map of the A1 antenna and B-line. All the sensors in the A1 an­ tenna were three-compo­ nent instruments. The B-line consisted of both single-component verti­ cal sensors (circles) and three-component (triangles) sensors. Se­ lected station names are indicated for the B-line.

data loggers brought the total n u m b e r of seis­ mic data c h a n n e l s recorded on Kilauea in January 1996 to 389 when all the loggers were operating. Over 4 0 GB of data were col­ lected during the month-long experiment. Data and Analysis The principal goal of the experiment was to record v o l c a n i c tremor and v o l c a n i c earth­ quakes. Such signals are especially c o m m o n at active v o l c a n o e s and have b e e n docu­ mented at over 160 v o l c a n o e s worldwide [McNutt, 1994]. The tremor signal during most of the recording period was weak, asso­ ciated with the steady, effusive lava flow from the Pu'u O'o eruption site in the Kilauea east rift zone. Shallow, long-period earth­ quakes b e n e a t h Kilauea c a l d e r a were re­ corded by the portable network. Twenty-five of the portable digital stations were still operating when over 500 earth­ quakes were recorded at Kilauea crater from 0 8 0 0 - 1 3 0 0 HST on February 1. It is likely that the portable units recorded many earth­ quakes that were too small to process through the routine HVO data analysis proce­ dures. T h e denser network, which consisted of both the telemetered digital stations and the portable data loggers c o m p l e m e n t i n g the HVO analog array, m a d e the February 1 intru­ sive earthquake swarm the best ever re­ c o r d e d at Kilauea. The additional bandwidth and dynamic range afforded by the digital field equipment offer a unique opportunity to analyze earthquakes associated with m a g m a migration and eruption. Hundreds of volcano-tectonic earth­ quakes were also detected by the HVO net­ work during the course of the experiment, including many earthquakes that o c c u r r e d b e n e a t h other parts of Hawaii. The working group will c o n t i n u e to inves­ tigate s o u r c e processes and the nature of seis­

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mic wave propagation under Kilauea using a range of data analysis techniques. Re­ searchers plan to determine precise event lo­ cations; perform frequency-slowness and correlation analyses of long-period events, tremor, and volcano-tectonic earthquakes; perform detailed s o u r c e modeling; and de­ velop fine-scale three-dimensional tomogra­ phy using both P and S waves. Other objectives include performing studies of the site, propagation and topography effects; and investigating the heterogeneity and scattering properties of the v o l c a n i c me­ dium using c o d a waves and t e l e s e i s m i c studies. T h e s e data and analyses will provide the most definitive view to date of v o l c a n i c earth­ quakes and tremor, and will serve as a b e n c h ­ mark for future studies. While there are already many tools available for data analy­ ses, this u n p r e c e d e n t e d collection of data will allow us to capitalize on new procedures developed in the future. Besides studying the data c o l l e c t e d in this January 1996 experi­ ment, the working group is planning another seismic survey in Hawaii for early 1997, prob­ ably n e a r Pu'u O'o. This will b e followed by a similar survey at a n o t h e r v o l c a n o — h o p e ­ fully an e x p l o s i v e o n e — i n the United States, J a p a n , or a n o t h e r country the follow­ ing year. Detailed seismologic investigations on v o l c a n o e s c a n greatly improve our under­ standing of how v o l c a n o e s work and how vol­ c a n i c disasters might b e averted through monitoring. Preliminary results of data analyses were presented at a special session of the 1997 meeting of the International Association of Volcanology and Chemistry of the Earth's In­ terior in Puerto Vallarta, Mexico. Repre­ sentative seismograms, detailed maps, site descriptions, and results of initial data analy­ ses will b e included in a U.S. Geological Sur­ vey Open-File Report ox Bulletin of the Earthquake Research Institute, University of Tokyo. In addition, a special issue of the Jour­ nal of Volcanology and Geothermal Research dedicated to results from this experiment is being planned.

Acknowledgments List of Participants: Y. Ida, T. Iwasaki, N. Gyoda, J . Oikawa, M. Ichihara, Y. Goto, T. Kurihara, M. Udagawa, K. Y a m a m o t o (ERI, Univ. of Tokyo); K. Y a m a o k a , M. Nishihara, T. Okuda (Nagoya Univ.); H. Shimizu, H. Yakiwara (Kyushu Univ.); E. Fujita (NEID, Tsukuba); B. Chouet, C. Dietel, P. Dawson (USGS, Menlo Park); P. Okubo, A. Okamura, M. Lisowski, M. Sako, K. Honma, W. Tanigawa (USGS, HVO); S. McNutt, D. Christensen, J . Benoit (Univ. of Alaska, Fairbanks); S. Kedar (CIT, P a s a d e n a ) ; T. Ohminato (GSJ, Tsukuba); G. Saccorotti (Oss. Vesuviano, Napoli); and S. Adachi (Hakusan Corp., J a ­ p a n ) . Funding for this experiment was pro­ vided by a grant from the J a p a n e s e Ministry

Eos, Vol. 78, No. 10, March 11, 1997 of Education to the Earthquake R e s e a c h Insti­ tute of the University of Tokyo. References Aki, K., S p a c e a n d t i m e s p e c t r a o f s t a t i o n a r y s t o c h a s t i c w a v e s , with s p e c i a l r e f e r e n c e to m i c r o t r e m o r s , Bull. Earthquake Res. Inst. Univ. Tokyo, 25, 4 1 5 , 1 9 5 7 . Aki, K., A n o t e o n t h e u s e of m i c r o s e i s m s in d e t e r m i n i n g t h e s h a l l o w s t r u c t u r e s of t h e e a r t h ' s crust, Geophysics, 30, 6 6 5 , 1 9 6 5 . D i e t e l , C , B . C h o u e t , K. Aki, V. F e r r a z z i n i , P. R o b e r t s , a n d R. K o y a n a g i , D a t a s u m m a r y for d e n s e G E O S array o b s e r v a t i o n s o f seis­ m i c a c t i v i t y a s s o c i a t e d with m a g m a trans­

port at K i l a u e a V o l c a n o , Hawaii, U.S. Geol. Surv. Open File Rep., 89-113, 171 pp., 1 9 8 9 . D i e t e l , C , B . C h o u e t , J . K l e i n m a n , G. d e L u c a , M. Martini, G. M i l a n a , J . P o w e r , D. H a r l o w , a n d R. S c a r p a , Array t r a c k i n g o f t r e m o r s o u r c e s at S t r o m b o l i V o l c a n o , Italy, U.S. Geol. Surv. Open File Rep., 94-142, 8 6 pp., 1 9 9 4 . Ferrazzini, V., K. Aki, a n d B . C h o u e t , C h a r a c ­ t e r i s t i c s o f s e i s m i c w a v e s c o m p o s i n g Hawai­ ian v o l c a n i c t r e m o r a n d gas-piston e v e n t s o b s e r v e d b y a n e a r - s o u r c e array, J . Geophys. Res., 96, 6 1 9 9 , 1 9 9 1 . G o l d s t e i n , P., a n d B . C h o u e t , Array m e a s u r e ­ m e n t s a n d m o d e l i n g o f s o u r c e s of s h a l l o w

23 Science Societies Issue Joint Call for More Federal Research Dollars PAGES 105-106

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In an u n p r e c e d e n t e d demonstra­ tion of unity, the leaders of 23 American scientific societies and umbrella organizations gathered on March 4 in Washington, D.C., to press the U.S. federal government for increased funding for scien­ tific research and to m a k e an investment in the nation's future. In a "Joint Statement on Scientific Research" addressed to President Bill Clinton and the Congress, the presidents of learned societies representing more than o n e million scientists, mathematicians, and engineers asked the government "to renew the nation's historical c o m m i t m e n t to scien­ tific research and education," and to reverse the d e c l i n e of federal investment in s c i e n c e and engineering. The American Geophysical Union was o n e of the signatories of the state­ ment.

"We strongly believe that for our nation to meet the challenges of the next century, a g e n c i e s charged with carrying out scientific research and education require increases in their respective research budgets in the range of 7% for fiscal year 1998," the coalition of scientific societies said in its statement. "Those a g e n c i e s include, a m o n g others, the National S c i e n c e Foundation, the National In­ stitutes of Health, the Department of Energy, the Department of Defense, and the National Aeronautics and S p a c e Administration." The 7% increase would "partially restore the infla­ tionary losses that most of the a g e n c i e s suf­ fered during the last few years," the coalition noted ( s e e Figure 1). By joining forces to m a k e the statement, scientists and disciplines that have c o m p e t e d with e a c h other in the past for federal dollars are now standing together in an interdiscipli­ nary union. "The fields of s c i e n c e have be­ c o m e so interdependent in recent years that a d v a n c e s in any o n e field are critically de­ pendent upon breakthroughs in other fields—frequently in fields that might s e e m completely unrelated," said Allan Bromley,

president of the American Physical Society and former s c i e n c e advisor to President George Bush. "In c o n s e q u e n c e , cuts in the support and level of activity in any o n e area are s o o n felt throughout the entire research enterprise." "What is remarkable about the joint state­ ment is not the statement itself, but that 23 sci­ entific societies have agreed for the first time to speak with o n e voice," said AGU President Sean S o l o m o n , who signed the statement on behalf of the Union. "The coordination of public policy messages a m o n g repre­ sentatives of the physical s c i e n c e s is long overdue." T h e a n n o u n c e m e n t of the Joint Statement on Scientific Research was generally well-re­ ceived by m e m b e r s of Congress, although s o m e m e m b e r s s e e the request as wishful

v o l c a n i c t r e m o r at K i l a u e a V o l c a n o , Ha­ waii, J . Geophys. Res., 99, 2 6 3 7 , 1 9 9 4 . McNutt, S. R., V o l c a n i c t r e m o r from a r o u n d t h e w o r l d , 1 9 9 2 u p d a t e , Acta Volcanoi, 5, 197, 1 9 9 4 . O i k a w a , J . , Y . Ida, a n d K. Y a m a o k a , S o u r c e s p e c t r u m a n d s o u r c e t i m e f u n c t i o n of vol­ c a n i c t r e m o r d e t e r m i n e d with a d e n s e seis­ m i c n e t w o r k n e a r t h e s u m m i t c r a t e r of Izu-Oshima v o l c a n o , J a p a n . J . G e o p h y s . Res., 9 9 , 9 5 2 3 , 1 9 9 4 . Y a m a o k a , K., J . O i k a w a , a n d Y . Ida, An iso­ tropic s o u r c e of v o l c a n i c tremor: observa­ tion with a d e n s e s e i s m i c n e t w o r k at Izu-Oshima v o l c a n o , J a p a n , J . V o l c a n o i . Geotherm. Res., 47, 329, 1991.

thinking, given the current budgetary climate in the United States. The new chairman of the House S c i e n c e Committee, Representative J a m e s Sensenbrenner (R-Wis.), noted in a March 4 inter­ view on C-SPAN that "increased spending on R&D pays dividends for all of us." But he cau­ tioned that while the leaders of the scientific societies are "well-intentioned," the major problem facing the country right now is the federal budget deficit. If the Congress and the Executive Branch can agree on a formula to b a l a n c e the budget, S e n s e n b r e n n e r s a i d , "I would h o p e that s c i e n c e is o n e of our top priorities." Rep. George Brown (D-Calif.), ranking mi­ nority m e m b e r of the House S c i e n c e Commit­ tee, added that "while there are several proposals and requests to increase spending on research, n o n e of those proposals identi­ fies how such increases will b e a c c o m m o ­ dated in a b a l a n c e d budget s c e n a r i o . Until you take that step, you are just playing with Monopoly money," he said. Brown also an-

PERCENT CHANGE IN FEDERAL S&T BUDGETS FY 1994 - FY 1997 (CONSTANT DOLLARS) PERCENT -10

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SOURCE: NATIONAL ACADEMY OF SCIENCES, JANUARY 16,1997] Fig. 1. When adjusted for inflation, the science and technology budgets of most federal have declined steadily since 1994, following nearly four decades of growth.

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