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THE PRESIDENT'S SCIENCE ADVISORY COMMITTEE
EXECUTIVE OFFICE BUILDING
WASHINGTON 25. D. C.
January 12, 1959
MEMORANDUM FOR The Honorable Christian A. Herter
The Honorable John A. McCone
The Honorable Donald A. Quarles
The Honorable Allen W. Dulles V
The Honorable Gordon Gray
The Honorable George Allen
SUBJECT: First Report of the Panel on Seismic Improvement
Attached for your :information is the first report of a special
Ad Hoc Panel on Seismic Improvement. This is the panel which
I proposed at the meeting of the group called together by Secretary
Herter on December 30, 1958 to discuss the implications of the
new data on underground. tests from Hardtack II.
The Panel which prepared the report was made up of the
following individuals:
Victor Hugo Benioff, Professor of Seismology, California
Institute of Technology
Hans A. Bethe, Professor of Physics, Cornell University
John Gerrard, Director, Data Systems and Earth Science
Research, Texas Instruments, Inc.
David Tressel Griggs, Professor of Geophysics, Institute
of Geophysics, University of California at Los Angeles
Jack H. Hamilton, Chief Engineer, The Geotechnical Corporation
Julius Paul. Molnar, President Sandia Corporation
Jack E. Oliver, Seismologist, Lamont Geological Observatory,
Columbia University
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Frank Press, Director, Seismological Laboratory, Division
of the Geological Sciences, California Institute of Technology
Carl F. Romney, U. S. Air Force
Kenneth Street, Jr. , Deputy Director, Livermore Laboratory
John W. Tukey, Professor of Mathematics, Princeton University
Lloyd V. Berkner, President, Associated Universities, Inc.
(Chairman)
In brief, the panel concludes that there are four possible methods
within the present state- of-the-art which might substantially improve
the capabilities of the Geneva system.
to prepare a quantitative analysis of the effect of these four
approaches on the capabilities of the Geneva system.
With this report available, a next step would be for
The individual members of the panel are continuing to study
in greater detail the various seismic techniques described in this
report, and in early February the panel will meet again to formulate
further recommendations for a research program designed to
evaluate the specific proposals, and to advance the state-of-the-art
in relevant areas of seismology.
For your information, I also include a separate memorandum
prepared by the panel concerning the value of a nuclear control
system to geophysical research.
The President has requested me to obtain any comments you
may have on the main report and tcDnsolidate them with those
received from Other interested departments and agencies. These
comments should be in the hands of this office not later than the
close of business Friday, January 16, 1959. Pending the President's
further consideration of the matter the panel report and memoranda
are both classified and privileged.
The President has asked that staffing be held to the highest
possible level.
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January 7, 1959
REPORT OF THE PANEL ON SEISMIC IMPROVEMENT
1. The Panel on Seismic Improvement (PSI), appointed by the
Chairman of the President's Science Advisory Committee, met in
Washington on January 6 and 7, 1959, to review measures whereby
it "would be reasonably feasible within the present state of seismic
technology to improve the capabilities of the system recomn-mended
by the Geneva Conference of Experts to detect and to identify seismic
events as either earthquakes or explosions without increasing the
number of manned control posts in the system. "
Z. The capabilities of the Geneva system with regard to under-
ground tests have recently been reevaluated by another Panel on the
basis of new data from the underground tests at HARDTACK II. The
PSI did not attempt to evaluate further the specific capability of the
Geneva System. The proposals recomMended herein would increase
the estimated capabilities of the Geneva System. It is noted that the
data on nuclear shots used in thetfe estimates was from Rainier and
HARDTACK II and thus has all the limitations of that small sample
of nuclear test conditions. The PSI has not concerned itself with
the possible seismic effects of nuclear tests under different conditions
or the possibilities of concealment by ecouping or other tec niques:
3. The Geneva System of seismic identification places principal
reliance on the assessment of a single phenomenon, i.e. the direction
of displacement of the first arrival of the P-wave in a specified net-
work of seismic instruments. The PSI considered a variety of seismic
phenomena and techniques which have been suggested to increase the
capability of the Geneva System without adding manned control posts,
including:
(a). Evaluation of the first motion of the P-wave with
aid of approximate inverse transfer functions.
(b) Surface wave phenomena using long-period instruments.
(c) Unmanned, auxiliary seismic stations.
(d) Larger arrays of seismometers at manned control posts.
(e) Improvements from increased knowledge of the
transmission properties of the earth by experience in
operation of the system.
(f) After shocks as a diagnostic feature.
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(g) Radiation asymmetry at the source.
(h) Use of computers in data analysis.
(i) Use of higher frequency seismic signals.
(j) Detectors on ocean bottom.
(k) Detectors in deep hole.
(1) Diagnostic possibilities of microseisms.
(m) Focal depth of disturbances.
5. On the basis of its review of the above techniques, the PSI
believes that the following four promising approaches are within the
present limits of technology and should be considered:
(a) Analysis of long-period surface waves. The capability
of the Geneva System for the identification as earthquakes of seismic
events equivalent to 5 kilotons or larger by the analysis of long-period
surface waves is conservatively estimated at 25% and may be much
larger.
(b) Network of unmanned auxilia y seismic stations. A
triangular network of such unmanned stations is suggested, spaced 170 km
apart between the stations of the 1000 km grid proposed in Geneva for
the seismic regions of the world. If this network were installed and
effectively operated, it would very greatly increase the capability of
the Geneva system for identifying as earthquakes those seismic events
occur ringin interior areas and corresponding in energy to underground
tests equivalent to one kiloton or larger.
(c) Larger arrays of seismometers at manned control posts.
It is reasonably certain that the replacement of 10 distributed seismometers
per control post as recommended by the Geneva Conference of Experts with
arrays of approximately 100 distributed seismometers would increase the
signal to noise ratio by a factor of from 1.5 to 2.5. This would substan-
tially increase the capability of the system to identify small seismic events
as natural earthquakes.
(d) Detectors in deep holes. A detection method which employs
a seismometer in a hole attaa depth of several thousand feet is being
investigated at the present time. The method offers possibilities for
improving the detestability of small signals by a factor of the order of
ten, provided that the technological problems of operating instruments
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at the required depths can be solved. The results to date are incomplete
but encouraging. If the factor of ten can in fact be achieved, it would
drastically increase the capability of the system to identify small seismic
events as natural earthquakes. More definitive results are expected by
mid 1959.
The proposals (a), (b), and (c), above, are discussed more fully
in the appendix attached.
6. The PSI invites attention to the fact that detection of aftershocks
by specially and immediately implaced seismometers can be used by an
inspection party as an aid in establishing that an unidentified seismic
event was in fact a natural earthquake.
7. The PSI believes that seismic research has not in the past been
supported as strongly as many other areas of science. Vigorous research
in seismology is certain to produce many improvements that cannot now be
predicted. It is certain that this would lead to an improvement in detection
capabilities. The PSI will shortly report its detailed recommendations
concerning research in seismology.
8. The PSI urges that sample detection networks be established
without delay as representative systems to disclose operational and design
problems and provide a firmer basis for the assessment of detection
capabilities.
96 The Geneva Conference of Experts recommended supplying
new instruments to the existing world network of seismic stations. The
PSI believes that this recommendation should be implemented within the
next year even if it must be done unilaterally by the U. S.
Lloyd V. Berkner (Chairman)
Victor H. Benioff
Hans A. Bethe
John Gerrard
David T. Griggs
Jack H. Hamilton
Julius P. Molnar
Jack E. Oliver
Frank Press
Carl F. Romney
Kenneth Street, Jr.
John W. Tukey
'. 'f': M TI I
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APPENDIX
1. Analysis of Long Period Surface Waves
Long-period seismograph data (periods greater than 5 seconds)
available from HARDTACK II and natural earthquakes suggest additional
criteria for the identification of seismic events as natural earthquakes.
In the yield range 5KT-23 KT, stations at distances up to at least 3500 kn.1
can provide the necessary data, in the absence of microseismic storms.
The capability of the Geneva System for the identification as earthquakes
of seismic events equivalent to 5 kilotons or larger by the analysis of long-
period surface waves is conservatively estimated at 25% and may be much
larger. Estimates of capabilities are based on observations with
instruments not designed for this purpose. The use of specifically
designed equipment should further improve the estimates of capabilities.
On the basis of present technology, it is concluded that the following
techniques are available:
a) Love-Rayleigh wave amplitude ratio. A preliminary study of
amplitude ratio of Love waves to Rayleigh waves for periods greater than
about 10 sec. from earthquakes and underground explosions has been
conducted at the Lamont Geological Observatory at Palisades, New York.
The results indicate that in the equivalent magnitude range 5 KT-23 KT
a single station at a distance of 3500 km or less can identify about 10%
of seismic events as natural earthquakes. Data from stations in appreciable
different azimuths are relatively independent and so increase the
probability of identification significantly but not above some as yet
undetermined limit.
b) Spectra of surface waves recorded on long period, horizontal
component seismographs. Data from Palisades, Pasadena, and Berkley
indicate a systematic difference in the long period spectra of earthquakes
and underground nuclear explosions. Although the effect is striking, it
is not possible to quote the capability of this method at this time except
to estimate that identification of earthquakes from a network of stations
is no worse than 10% and the upper limit is open.
The possibility exists that further results can be obtained in the
immediate future by additional studies of the amplitude ratio for
Love-Rayleigh waves and its aximuthal dependence for earthquakes.
This will provide additional data to verify the estimate of 10% identifi-
cation of earthquakes and examine the possibility of increasing this
figure.
II. Network of Unmanned Auxiliary Seismic Stations
Interpolation of unmanned automatic seismic stations into the
grid of control posts of the Geneva plan gives promise of providing
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UUNNIJLIVIOAL
significantly greater information on weak seismic events, corresponding
in intensity to one kiloton. A triangular network of such unmanned stations
is suggested, spaced 170 km apart between the stations of the 1000 km
grid proposed in Geneva for the seismic regions of the world. In such a
network, a one kiloton shot coupled seismically to the same degree as
Rainier, Logan, and Blanca would give 50 millirnicron amplitudes or
higher for first motion of P-waves at nine stations on the average. Thus
data from single vertical-component seismometers disposed in such a
network would suffice to detect first motion with reasonable certainty.
The practical problems of installing such a network may be estimated
by noting that the spacings mentioned above imply having 35 auxiliary
stations per main station and that the maximum communication distance
between a main and auxiliary station is 600 km. Each auxiliary station
would require a seismometer, a recording device (for providing a permanent
record), a clock, a radio transmitter, a source of electric power, and
probably a data storage device which will permit compressed data trans-
mission as required. The cost of the technical apparatus needed for a
single station, when manufactured in large quantities, might be ten to
thirty thousand dollars. Access roads (or helicopter pads), installation
and related costs may run the total costs up considerably higher, depending
on local conditions. Periodic maintenance and record retrieval would
probably be required at 30 to 60 day intervals.
The need for this network of auxiliary stations is clearly greatest
in the areas of the world where earthquakes occur with high frequency.
It might be acceptable to limit application of the network only to these
areas, possibly 20% of the land surface of the world. Also one could tailor
power and communication arrangements (possibly using wire lines in some
places) according to the local facilities available.
If this network could be ''installed and effectively operated, it would
very greatly increase the capability of the Geneva System for identifying
those seismic events which are earthquakes, occurring in interior areas
and corresponding in intensity to underground one kiloton or larger shots.
The practical difficulties of installation, maintenance, and operation of the
system, especially in remote areas, should not, however, be underestimated,
and the possibilities for occasional spoofing must be recognized.
III. Larger Arrays of Seismometers at Manned Control Posts.
On the basis of present knowledge, replacing 10 distributed
seismometers in a 3 km x 3 kin square as recommended for each control
post in the Geneva System by 100 distributed seismometers in the same
square would affect the signal to noise ratio at frequencies near 1 cycle
0I14 tIr~ n: i.iT1Ad1
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per second as follows, using specifiable techniques:
(1) It is reasonably certain that an improvement at most stations
by a factor of between 1.5 to 2- 5 will be obtained;
(2) There is reason to hope for improvements in the range
from 2.0 to 2.5;
(3) Increases from 10 to 10k stations should provide improvement
by a factor from k0.2 to [c0.4 for k = 10.
(4) Data which can be obtained within one month will provide a
much firmer estimate of what may be expected. The data to be
obtained include, most importantly, data on coherence of noise at
station separations of 150 to 1500 feet, and secondarily, data on
dependence of typical noise levels on wind velocity.
(5) When more is known about noise characteristics, it may well
be possible to gain further improvement by applying other analytical
techniques to a 100 seismometer array.
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i8.7lua~ry Ar I9S)
3*. NIt..,Ut": tor i.`>r. J. :t J.Ui#n.. Jr.
aect:, Vl> a of l tt leaa9r 'rest control System to t eaexcarch in (:seeophys?cs
ra connection with its current review of measures which would
irrprove the iei.srnie capaiatlities ox the detection system reeo==.
r )eended by the Geneva t,,onterence of ha rts, the Panel on +ialmic
Xnx-proverrent, appointed by the t;hairrnaan of the :tVrovident's Science
Advisory Cort-m ttteer wis;fines to call specixtc attention to the verse ei
*?uc:h a detection network to researc:ta in geophysics. This statement
as submitted separately trorn the initiak report of the dated
1 :January. since the teuhjeect fifes ouisieiee the immediate charter of
'.ate i-. 'i. iF
The network proposed by the Cxeneva c.;onferencee of 1!.xperts
or monitoring nuclear explosions oat groat potentiality for
-re search in geophysics. The AJ Y program demonstrates how major
advances can be made by world-wior observations with a network
ej u.niforrn stations having instruxeaents of advanced design
Rcienti.fic r?e sultae which can be sntlcipatentl u maaaay tied ds
r? geo*=taysics trorr: lull exploitation of the (en.eva network would
wierii the estabtistar,eent of such aa. not for atclenti tc purposes xione.
;ire are heist equtppea to assess the curatr'tout ions to geophysics o
the solid earth.
,ur resent picture of the interior of the earth has been pieced
f:ogether Largely from,, scraps of it orn~aatreaas caart+td from seismic
waves which have traversed me depths to varying degrees. ti-arrent
beories of the genesas and constitution of the earth, of the origin
=i)i continents and ri oiuatains staves cry ear an order 0f magnitude
increase in the precision eft sei,emit data to provide confirmation
or dispre:c-#.
ihe establishment of the :nigh uality seisrrtic stations proposeeu
by the G:.:eenrttia onterencee of .r.:xpera.s-i1 exploited for geophyeac&i
search (which woeitd not in any waxy interfere with normal operation
tit the nett-would hula the prcm7'ms s4~ oa advancing our seismological
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it-.- to a. very large degree, If this not were au rreenteed in
th various ways proplosed by the pireserlt conference, and if the
research and development programs discussed here were actively
puraueri, the advance wcrild kre spectacular. if this net, suitably
a Lagrr,enteca by portable stationm, were test.:.l by large H. L. and
occasional nuclear * itots unc e r international auspices, then the
must drean, o U. se scr~~alogtats a ulcl have carne true.
"h.e_ above has assumed that the seisrrsic_ detection not was
ploited for geophysical research purposes. It is our tirin
heiiee that unlesea this possibility isi firmly built into the treaty,
Glor,ipetent seisn.ologists will not be attracted into the irate rra.atts~nal
uxgaun which administers the net. lx corrspetent people are not
so attracted the )otentiallittees of the net for routine seismic
-.ietectior, of earthquakes and eacpiasions will never be realized,
1,1:-rd V. Berkner (t.;:,hairnian)
V i c.tor H. l3enioff
L~ 'anc A. ts.t1w
_iCO-rn Gerrard
i-La'=id r. t;riags
Jat.k: rVi. Hamilton
+.;aiatrs J, SAolnar
I-: ?diver
r'xnx dress
;414 e'. htarr^ney
krnrieth Street, Jr.
3 ">hn VV. ttitie ee;'tr
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