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1302
The Hawaiian Volcano Observatory (HVO)
United States Geological Survey
P.O. Box 51
Hawaii National Park, Hawaii 96718
USA

Telephone :	(1) 808-967-7328
Telefax :	(1) 808-967-8890
Scientist in Charge:	Dr. Jim Kauahikaua
Email :	jimk@usgs.gov
Website :	hvo.wr.usgs.gov/

Scientist in charge: Dr. Jim Kauahikaua

Chief of Operations: Steve Brantley

Scientific staff:

Seismology:

Paul Okubo
Jennifer Nakata
Wil Tanigawa
Alvin Tomori

Non-seismic Geophysics:

Jim Kauahikaua
Gary Puniwai

Ground deformation:

Arnold Okamura
Maurice Sako
Asta Mikilius
Peter Cervelli

Geology-Petrology:

Rick Hoblitt
Christina Heliker
Tari Moulds

Don Swanson

Gas geochemistry:

Barry Stokes, Jeff Sutton

Technical support:

Electronics:

Ken Honma
Allan Largo
Renee Ellorda, Bruce Furukawa

Computer:

 

Photographer:

 

Librarian/Photo Archivist:

Jan Takahashi

Office:

Marian Kagimoto
Pauline Fukunaga
Irene Tengan

SEISMOLOGY

HVO maintains an extensive radio-telemetered seismometer network on the island of Hawaii. Since 1984 the network has consisted of 51 stations; 10 are three-component, and 41 are vertical only. The coverage is most complete on and around Kilauea volcano. With the exception of self-contained systems at Uwekahuna and Hilo stations, all seismometer signals from the short period network are telemetered to the observatory for recording. A detailed history of each station is given in F.W. Klein and R.Y. Koyanagi, Hawaiian Volcano Observatory Seismic Network History 1950-79, U.S. Geological Survey open File Report 80-302, 1980.

In addition to the standard stations, optical seismographs are maintained at Uwekahuna (HVO), Hilo, Maui and on Oahu (Honolulu and Kipapa stations are operated by the Pacific Tsunami Warning Center). The less sensitive optical records are used primarily for amplitude measurements for magnitude calculations to supplement readings from the high-gain stations. The paper (optical) records as well as the 16 mm Develocorder microfilm are archived at HVO.

Each telemetering station has a voltage controlled oscillator (VCO) for FM multiplex transmission to HVO via (either hardwire or) radio. These telemetering stations are now all of Type 1, the (OEVE) standard system used in all USGS seismic networks. After discrimination, the analog signals from 36 stations are recorded on two Develocorders using 16 mm microfilm. FM signals from the telemetering network are also recorded directly on one-inch magnetic tape. Selected larger events are copied onto condensed FM library tapes which are currently archived in Menlo Park and archived in digital form at HVO as part of the routine location processing.

In 1985, a computer-based seismic data acquisition/processing/archiving system, the CUSP (Caltech/USGS Seismic Processing) system, was introduced at HVO. The CUSP system is also in use at the USGS earthquake centers in Menlo Park and Pasadena as well as the University of Nevada at Reno, with some differences to accomodate differences in computer hardware and seismological setting. At HVO, CUSP is presently run on a DEC VAX 11/750 in the DEC VMS operating system.

A total of 80 data channels from the 51 telemetered stations are analyzed in CUSP. Discriminator outputs from the telemetered data channels are passed through an analog-to-digital convertor. The digital data are then set for processing in a number of stages. Automated data analysis begins with seismic event detection to trigger data storage. If no events are identified, the digital data passes through the computer memory without being stored on disk, so that the digital data set is comprised of a series of discrete events rather than a continuous time series. Following an event trigger, arrival times for seismic P-waves are automatically estimated where possible and these data are used to estimate preliminary earthquake location and magnitude. For display purposes, as soon as location and magnitude information becomes available, epicenters are plotted using an Amiga personal computer. Data analysts examine all of the declared and stored events to improve estimates of arrival times determined automatically, to add more arrival time information for both P- and S-waves, and to re-locate the hypocenters based on this augmented set of arrival times. Over 10,000 earthquakes are processed by using CUSP each year, and final catalog information is derived by combining CUSP data with the standard HVO earthquake location program HYPOINVERSE (Klein, USGS Open-File report 89-314). Published annual seismicity summaries typically contain over 2,000 earthquakes of magnitude greater than 1.5.

Develocorder films are scanned on a daily basis for earthquakes and volcanic tremor. Daily earthquake counts are assembled for defined regions beneath the island of Hawaii. Earthquakes are also classified on the basis of frequency content of the signals. It is thought that long-period earthquakes with predominant frequencies from 1 to 5 Hz are associated with magmatic processes and that microearthquakes with higher frequency content are associated with both magmatic and tectonic processes.

The emphasis in both station coverage and detailed data analysis is on the highly active south half of the island of Hawaii. Hundreds of earthquakes too small to locate are counted daily, and the set of located earthquakes in the Kilauea region is nearly complete above magnitude about 2.0. Many smaller events are located also. Substantial effort is made to locate earthquake elsewhere on the island and within about 150 km of the island. Such coverage cannot be as complete as on the south flank, but nearly all events above magnitude 3.0 to 3.5 are located. Data are presented in a seismic summary published quarterly (up to 1974) and yearly (since 1974); copies are available upon request from HVO.

The crustal model used is specified by velocities at 4 depth points. Velocity at any depth is given by linear interpolation between points and uses a homogeneous half-space below.

Two empirical sets of stations delays or corrections were used in the locations. Delay model 1 is used for events on Kilauea and its south flank, and delay model 2 applies to the rest of the island and offshore earthquakes. The delay models are in fact separated by a circle of radius 34 km centered at 19°22’N and 155°10’W.

Magnitudes for most events were computed using both recorded amplitudes on low gain or Wood-Anderson stations, and signal or coda duration on selected short-period vertical stations.

Duration magnitudes are determined from the length of signal in seconds read from the Develocorder viewer. This time, also called the " F-P time " is measured from the first P arrival to the point where the earthquake signal had decayed nearly to the noise level. A bilinear relation is an appropriate fit to the data sample and is used to compute all duration magnitudes. Duration times are read only from Type 1 seismographs. Because duration magnitudes are relatively insensitive to station response and can be determined using the high-gain short-period stations, it is felt that duration magnitudes are more accurate and complete at the lower magnitudes (below 2).

The equations used in magnitude determination are:

duration < 210 sec M = - 5.2 + 3.87 log (F-P) + 0.13 Z + 0.037 D

duration < 210 sec M = -.905 + 2.026 log (F-P) * .013 Z + .0037 D

where Z and D are the depth and epicentral distance in km, respectively.

NON-SEISMIC GEOPHYSICS

Electrical Studies

Self-potential (SP) monitoring shows high amplitude-positive anomalies associated with intrusive and eruptive zones. Mapping delineates zones of intrusion, some of which are seemingly transparent to non-electrical monitoring techniques. The following SP array are in operation:

- one telemetered array on Kilauea’s upper east rift zone,

- 15 km of nailed monitor line on roads in the upper east rift zone, repeated yearly,

- 4 km of nailed monitor traverses on Kilauea’s middle east zone, repeated yearly,

- 14 km of nailed monitor traverses on Kilauea’s southwest rift zone, repeated when other monitors indicate intrusive activity in areas near any monitor line.

Controlled source electromagnetic (CSEM) monitor:

- responds to shallow intrusions (< 2km depth) near the vertical magnetic field sensors (Hz),

- four vertical magnetic field sensors now emplaced, two at Kilauea summit and one each in the upper parts of each rift zone,

- computer controlled operation, sampling on 50 percent duty cycle allows about 10 data sets/day,

- planned expansion to 3 components (Hx, Hy and Hz).

Gravity Monitoring

Gravity studies show changes in the gravitational acceleration due to elevation and subsurface mass changes:

- gravity is measured at least annually at 19 benchmarks on the summit and eastern flanks of Kilauea. Precision is ±10 µgal,

- another 20 benchmarks are to be monitored at Mauna Loa summit and southwest rift zone, and Hualalai,

- a real-time cryogenic gravity meter records gravity every two minutes at the Hawaiian Volcano Observatory. Precision is 0.1 µgal.

 

GROUND DEFORMATION

The surface deformation program HVO utilizes a variety of techniques and instruments in monitoring the active volcanoes of Hawaii. Extensive geodetic network encompass both Kilauea and Mauna Loa, and a lesser array covers Hualalai.

Changes in slope are measured at 110 small aperture (40 M) spirit-level tilt stations located in the summit region and rift zones of the three active volcanoes. The measurements are taken with Wild levels and rods. The rods (3) are three meters in height and have supporting stays. The Wild levels include one N-3 and a pair of NA-2 with parallel micrometer plates.

The spirit-level tilt method replaces the older but more precise portable watertube system as the primary tilt monitoring technique. However, eight watertube field stations still exist on Kilauea and can be remeasured at any time with the two remaining sets of HVO-made tiltmeters. Two short-base watertube stations are permanently installed in seismic vaults and are read periodically.

Six continuously recording electronic tilt stations are currently in operation on Kilauea and Mauna Loa. One of the stations has a uniaxial mercury capacitance Ideal-Aerosmith tiltmeter with a one seismic vault. The other stations have biaxial tiltmeters which measure the differential resistance created by a spirit bubble. Most of the spirit bubble tiltmeters are borehole, and a few are platform instruments with outputs of 20-40 millivolts per microradian. Except for the Ideal-Aerosmith mercury capacitance instrument, which is hardwired to the Observatory and recorded on an analog strip chart recorder, all tiltmeter outputs are digitally radio-telemetered to the Observatory and recorded on magnetic diskettes.

Over 750 lines comprise the trilateration/horizontal strain network established and measured by the Hawaiian Volcano Observatory. Thirty-one lines on Kilauea and 25 lines on Mauna Loa have permanently mounted reflectors. The inventory of electronic distance measurement (EDM) equipment include 1K&E Rangemaster III, 1 K&E Ranger V, 1 HP model 3808A, 1 HP model 3850A, 1 AGA model 8 geodimeter, 87 retroreflectors, 10 high precision altimeters, 10 digital thermistors, and a number of tripods and optical tribrachs. The EDM surveys are conducted at various time intervals, mainly dependent upon the activity of the volcanoes.

Vertical changes on the volcanoes are monitored on a number of level line networks that total nearly 400 kilometers in length. The various level networks are measured at irregular intervals with areas of greatest change surveyed more frequently. Two pairs of 3 meter height Wild rods with Invar strip and 3 NA2 Wild levels are the equipment used in leveling operation. On networks that are frequently reoccupied, all turning points are nailed and all setups are marked. Recording is done electronically.

In conjunction with the level surveys, gravity and sea level measurements are also taken. Nearly 200 gravity stations on the island are measured with 2 LaCoste G meters. Three tide stations are occupied in the spring of each year with Stevens mechanical tide gauges.

In addition to the 16 sites monitored with continuously recording GPS receivers, about 120 sites are surveyed using static GPS survey techniques every year. We expect the number of these infrequently occupied GPS sites to grow as we implement short-occupation and kinematic-survey techniques. NASA Gipsy-Oasis software is used to obtain position solutions for all static surveys. We use Rapid Service and final orbits provided by NASA's Jet Propulsion Laboratory in our data reduction. Solutions provide positions accurate to a few millimeters in the horizontal components and about a centimeter in the vertical component.

The remaining equipment inventory at the Hawaiian Volcano Observatory include 2 surveying transits and 2 theodolites.

GEOLOGY-PETROLOGY

Geological monitoring of Kilauea and Mauna Loa volcanoes includes visual surveillance of erupting areas (currently the east rift zone of Kilauea), time-lapse photography of the vent area, lava sampling and temperature measurements, mapping new lava flows, petrographic and geochemical analysis of sampled lavas, studying the development of the lava tube systems, and evaluation of the hazard posed by lava flows to inhabited areas. Ongoing research covers the geological significance of long-lived Kilauea eruptions, the history of observations on Hawaii’s active volcanoes, and the volcanological constraints on melting and magma accumulation within the Hawaiian hotspot.

 

GAS GEOCHEMISTRY

The ongoing gas geochemical research at the Hawaiian Volcano Observatory is focused on the geochemistry of present-day degassing at Kilauea. The research addresses both eruptive and noneruptive degassing. Gas monitoring provides geochemical data at all stages of the degassing cycle, including pre-eruptive, syneruptive and posteruptive. The goals of the program are as follows:

(1) to provide baseline gas geochemical data for assessment of hazards at degassing sites,

(2) to carry out special monitoring, field experiments, and modeling related to active and potentially active degassing volcanic areas,

(3) to develop and test gas monitoring techniques,

(4) to synthesize the results of the above work and examine its implications for environmental impact, biogeochemical cycles, climate change, and other broad areas of earth science research.

Monitoring of summit SO₂ flux at the summit of Kilauea (COSPEC) occurs 3-5 times weekly. Monitoring of SO₂ emissions from eruptive vents in middle east rift zone occurs approximately once every two months. COSPEC gas monitoring which began in 1979, is allowing us to better understand and characterize the mechanism of outgassing of magma temporarily stored in the shallow reservoir beneath the summit at Kilauea. In addition, we are currently working on satellite imaging experiments for gas plumes at both the summit and rift zones of Kilauea. " Ground truth " in situ experiments of the SO₂ emission rates are made while the SO₂ in the plume cloud is being imaged with a satellite-based UV spectrometer from space. We have expanded our gas sampling program of the carbon/sulphur ratios at summit fumaroles, which occurs 3-5 times weekly. Summit fumaroles are being sampled to compare carbon-to-sulfur ratios of established sites at the crater rim, and those within Halemaumau crater. Finally, we are working to identify the various components of volcanic smog (or " vog ") on the Big Island of Hawaii. The study will describe primary and secondary pollutants; the research will also determine diurnal and seasonal variation of respirable particulates of concern to public health.

 ELECTRONIC AND COMPUTER

HVO has a fully operational electronic laboratory to support instrument development and maintenance. The present computer configuration is two VAX 11- 750 mainframes, 2 SUN workstations (plus one additional SUN workstation for GIS applications), networked to PC’s and Macintosh workstations.

 

PHOTOGRAPHY AND LIBRARY

HVO has a professional staff photographer (35 mm still and large-format aerial photography) and a cooperative arrangement to obtain video footage of eruptions. Movie film is no longer taken at HVO. All photographic images are stored in a controlled environment.

HVO has a special purpose library covering all material on Hawaii’s active volcanoes from 1779 (Cook’s voyage of discovery) to the present. We maintain a large number of subscriptions to earth science journals and limited collections of books on volcanoes elsewhere in the world and general information on volcanic and seismic hazard.

 

GENERAL PUBLICATIONS ON HVO AND HAWAIIAN VOLCANISM

Free by writing to HVO

Heliker, C., Griggs, J.D., Takahashi, T.J., and Wright, T.L., 1986, Volcano monitoring at the U.S. Geological Survey’s Hawaiian Volcano Observatory: U.S. Geological Survey General Interest Publication, 71 p.

Heliker, C., 1990, Volcanic and Seismic hazards on the Island of Hawaii: U.S. Geological Survey General Interest Publication, 48 p.

Order from Hawaii Natural History Association, P.O. Box 74, Hawaii National Park, HI 96718 (Price does not include shipping).

Books:

Tilling, R.I., Heliker, C., and Wright, T.L., 1987, Eruptions of Hawaiian Volcanoes : Past, present, and future: U.S. Geological Survey Pamphlet, 547 p. Price (US) $4.00.

Wright, T.L., and Takahashi, T.J., 1989, Observation and Interpretation of Hawaiian volcanism and seismicity 1779-1955: An annotated bibliography and subject index : Honolulu, University of Hawaii Press, 270p. Price (US) $30.00.

Decker, R.W., Wright, T.L., and Stauffer, P.H., (eds), 1987, Volcanism in Hawaii (2 vols): U.S. Geological Survey Professional Paper 1350, 1667 p. Price (US) $95.00.

Bevens, D., Takahashi, T.J., and Wright, T.L., (compilers), 1988, The early serial publications of the Hawaiian Volcano Observatory (3 vols): Hawaii National Park, Hawaii Natural History Association, 3062 p. Price (US) $65.00.

Videos:

Inside Hawaiian Volcanoes: produced by Smithsonian Institution in collaboration with U.S. Geological Survey and Maurice Krafft, 25 min. Price (US) English, beta or VHS, $29.50; PAL, $39.50.

Kilauea: Close-up of an active volcano: produced by Ka I’o, John Kjargaard, videographer, 30 min. Price (US) English or Japanese, Beta or VHS, $29.50; PAL, $39.50.

 

Contact information updated August 2004; other information updated November 1996

   

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