Close-In Subsurface and Surface Shock-Wave Measurements in Scroll Event

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This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. Close-In Subsurface and Surface Shock-Wave Measurements in the

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency Portions of this document may be illegible in electronic image products. Images are produced from the best available

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This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein donot necessarily state or reflect those of the United States Government or the University of California,and shall not be used for advertising or product endorsement purposes. This report has been reproduceddirectly from the best available copy. Available to DOE and DOE contractors from theOffice of Scientific and Technical InformationP.O. Box 62, Oak Ridge, TN 37831Prices available from (615) 576-8401, FTS 626-8401 Available to the public from the National Technical Information Service U.S. Department of Commerce

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ropriatc ciasUfication level or indicate Unclassif non veriling thts in the correct dccument ct model) IN THE SCROLL EVENT AEC RESEARCH AND DEVELOPMENT REPORT

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Construction and Emplacement of Instruments • • 3 Acceleration and Velocity Measurements . 5 Calculated Velocity and Displacement . 17 Calculated Velocity and Displacement . . 21 Summary of Subsurface and Surface Data • • • 21

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IN THE SCROLL EVENT The Scroll Event was a seismicdecoupling experiment conducted at the Nevada Test Site. Subsurface measurements included stress history, shockfront time of arrival, acceleration, and velocity; surface measurements consisted of acceleration out to 610 m. The slifer instrumentation in the device-emplacement hole indicated that the explosive performed satisfactorily. The instrumentation on the device horizon (229 m) indicated that the medium around the device-emplacement hole attenuated the acceleration from more than 9286 g's at 32 m to 6 g's at 76 m. Sixteen of the 48 channels of information were lost because of unusual electromagnetic effects at detonation time. Acceleration and velocity information was obtained from six of the eight instrumented locations. The objective of the shock-wave experiment was realized. The Scroll Event was a nuclear detonation designed to determine the seismic porosity geologic medium. The device was emplaced at a depth of 229 m in an uncased hole (U19n) at the Nevada Test Site. Scroll was detonated on April 23, of the emplacement hole were longitude elevation of the hole collar was 2059 m above mean sea level. were performed by K Division, Lawrence Radiation Laboratory, Livermore. The primary purpose of the instrumentation was to experimentally define the seismic source for calculational comparison. The experimental results reported here are interpreted and compared with the

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o Acceleration and velocity gage Fig. 1. Diagram of the subsurface instrument network employed in the Scroll Event.

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Table I. Stratigraphic sequence at the Stratigraphic and lithologic Timber Mountain tuff Rainier Mesa member (upper) 0 to 128 Ashflow tuff; compound cooling unit; partially to densely welded; vitric todevitrified; brown to gray to maroon or black. Rainier Mesa member (lower) Ashflow tuff; nonwelded to 128 to 152 partially welded; pink to Ashflow, ashfall tuff; nonwelded; bedded; some units reworked; lithic rich;buff to pinkish gray (in this report, this unit is referred to as the "lowAshflow, ashfall tuff; partially welded, generallyzeolitized; some units reworked; pinkish gray Vitric; pale reddish gray aTotal depth of exploratory hole. calculated predictions given in a separate report.The subsurface materials at the siteare welded tuff, low-density ashfall tuff, zeolitized tuff, and rhyolite. Table I shows the geologic layers of the site. A more complete description of the geology is contained in Ref. 2. Geophysicalmeasurements and physical-property measurements of the site materials aredescribed in detail in Ref. 3. Three satellite instrument holes weredrilled south of the device-emplacement hole at distances of 30 m (U19n-1), 76 m emplacement hole and the satellite holes contained instruments designed to measur shock-front velocity, stress history, particle velocity, and particle acceleration.Surface instrumentation included one vertical and two orthogonal horizontal measurements of acceleration at ground zero (GZ) and at distances of 229 m and 610 m south of the GZ. Figure 1 shows the Scroll instrumentation locations. Construction and Emplacement of The nuclear explosive was emplaced in a 30-in.-diarn uncased hole at a depth of 229 m. The explosive and diagnostic canisters were lowered with a 4.5-in.- diam well casing. The device hole was stemmed with dry Overton sand with a 12-m-long grout plug centered at a depth of about 131 m. All of the holes were drilled with a vacuum technique in order to avoid introducing water into the medium and to minimize sloughing of the hole in Orientable instrument canisters were emplaced in the three satellite holes on 3.5-in.-o.d. fiberglass tubing. The transducer section of each canister conthe azimuthal direction of the canister.

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The transducer section was rotated to theproper azimuth by a motor fixed to the lowering tube (see Fig. 2). The fluxFig. 2. Diagram of a typical instrument meter readings were monitored and the motor controlled from the surface. The canisters were grouted into position with at least 8 m of medium-matching grout above and below the assembly. The re-maining sections of the instrument holes were stemmed with dry Overton sand.The Waterways Experiment Station of the U. S. Army Corps of Engineers developed and supervised the emplacement of the media-matching grouts. Appendix Agives the compositions and properties of The curing temperature of the grout sembly in Ul9n-3 reached at least 155°F. This temperature caused the two radial accelerometers at this location to fail. The high temperature apparently resulted from a larger-than-expected volume ofgrout caused by sloughing of the hole. All other grout sections stayed below 125°F during the curing process. Four tourmaline stress transducers were placed at a depth of 218 m in satellite hole Ul9n-1. Two units were oriented to measure the radial stress component of the compression wave and two to measure the tangential stress component. The crystal units were pregrouted in the orientable canister and were radiographed to verify that the gages were in the proper position and that the grout was competent. The radiographs indicated many gaseous voids in the grout, but the test schedule prevented replacement of the assembly. The signal of each transducer was changed to a frequency-modulated carrier by a

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Fig. 3. Layout of the stress-history instruments in satellite hole (VCO) about 45 m above the transducer location. Figure 3 is a block diagram of the stress-history instrument network, and Table II gives pertinent stressAcceleration and Velocity Measurements instruments were installed at five locaacceleration measurements in Ul9n-1 Table II. Stress-history transducer ometers manufactured by the Endevco Corporation. Velocity measurements in U19n-1 consisted of velocity gages made by Sparton Southwest, Inc., and of an electrical integration of the accelerometers. The VCO's for the velocity gages and accelerometers were inside the transducer canister. The Sparton variable-reluctance velocity gages were demodulators in the canister. The VCO's were potted with a special shockabsorbing epoxy. Figure 4 is a block diagram of the instruments in the Ul9n-1 velocity and acceleration package. Satellite hole U19n-2 was instrumented with accelerometers and velocity gages at the device horizon (Fig. 1). Two radial accelerometers and two radial velocity gages were installed in the orientable canister. One accelerometer was electronically integrated within the canister for velocity information. Satellite hole Ul9n-3 was instrumented at three locations to measure velocity and acceleration (see Fig. 1). The system located at the device horizon included one vertical accelerometer, one radial accelerometer, and one radial velocity gage. In addition, the signal from the radial

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To recording trailer To working point Fig. 4. Diagram of the velocity and acceleration instruments in satellite hole Ul9n-1

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accelerometer was integrated by an operational amplifier in the canister for The second system in Ul 9n-3 was located at a depth of 363 m. The canisterincluded a horizontal and a vertical accelerometer, a radial velocity gage, and amplifiers for integrating the acceleromeThe deepest instrumentation in Ul9n-3 was placed in the rhyolite medium at adepth of 607 m; it included two horizontal accelerometers, two vertical accelerometers, two radial accelerometers, and tworadial velocity gages. In addition, one of the radial accelerometers was elec-tronically integrated.The accelerometers in 1J19n-2 and Ul9n-3 were bridge-type instrumentsmanufactured by Statham Instruments, Inc. The velocity gages were piezoelectricand were supplied by the Consolidated Electrodynamics Corporation. Some of the accelerometers were emplaced so that negative going signals were produced. The ments were at the ground surface. Shockhardened operational amplifiers were used on each Statham accelerometer at the transducer. Figure 5 shows the typicalinstrument layout for the Ul9n-2 and Ul9n-3 installations. Table III summarizes the gage information for the subsurface velocity and acceleration instrumentation. The shock-front velocity was measured with two 53-m-long slifers emplacement hole. Both of the resonant cables were air dielectric heliax; one was 1/4 in. in diameter, the other 3/8 in. in diameter. The shorted end of the cable was placed 3.5 m from the working point; the shorted end of the other cable was placed 2 m from the working point. The slifers were electrically isolated from the device-emplacement pipe. The slifer cables were grouped with other device cables but were kept on the outside of the bundle. The first 9 to 12 m of each sliferlay in a metal tray along the diagnostic canister. The entire length of both slifers was stemmed with dry Overton sand. satellite hole U19n-1 were instrumented Fig. 5. Typical layout of the instruments used in satellite holes Ul9n-2 To recording trailer

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Table III. Summary of subsurface velocity and acceleration instrumentation. Gage type a to working point solidated Electrodynamics Corporation; and Statham = Statham Instruments, Inc. The Endevco and Statham instruments are accelerometers, the others are velocity gages. cAccelerometer electronically integrated for velocity information. dpC/pg = peak coulombs per peak acceleration. Brass shell Ceramic crystal Fig. 6. Cross section of a time-of-arrival PZT sensor.

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To recording trailer Fig. 7. Diagram of a PZT sensor "string." accelerometers. The VCOls for the time of arrival. Each "string" contained accelerometers were located near them. five such sensors. Each sensor was a Table V summarizes the types, ranges, ferroelectric, radially poled cylinder of sensitivities, and locations of the sur-PZT-4 material. The sensors were constructed as shown in Fig. 6 and instru- Table IV. Location of the shock-wave mented as shown in Fig. 7. Each "string" time-of-arrival sensors. had a downhole VCO for signal conditioning, Uphole Table IV gives the position of each sensor distance Radial relative to the working point, from distance were placed on the surface at the GZ and at positions 229 m and 610 m due south of the GZ. One vertical and two orthogonal horizontal component measurements were made at each location. Figure 8 shows the method of mounting the PZT-4 is a trade name for a ferro-electric material manufactured by the

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Micarta mounting block Accelerometer working point Fig. 8. Mounting of surface accelerometers. Table V. Summary of surface accelerometer installations.

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Significant stress signals were recorded by three of the four stress gages at 32 m (see Figs. 9 and 10). The signal from component transducer) was negative and did not have a significant amplitude. Stress-precursor signals were not recorded by all of the gages because of gas voids in the grout near some of the transducers. All of the signal cables were severed before the stress histories were complete. Table VI summarizes the stressAcceleration and Velocity celerometers in U19n-1 indicated higher accelerations than the anticipated 29,400 celerometer No. 1 lost continuity at 63,700 m/sec2 (6500 g's). The signal for accelerometer No. 2 saturated the VCO and it lost continuity very soon after saturation occurred. Figure 11 shows these Fig. 9. Stress-history signals at a radius of 31 m.

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Oscilloscope traces of stress-history signals at a radius of 31 m. Table VI. Summary of stress-history signals at 32 m. Transducer No. Signal time of arrival(msec) Peak stress(kbars) Stress component aTime of arrival of precursor signal.

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Fig. 11. Oscilloscope traces of acceleration signals at a radius of 31 m. Fig. 12. Oscilloscope trace of an accel-eration signal at a radius of76 m. signals. The Sparton velocity gages failed because their maximum range was exA number of the velocity gages and accelerometers in satellite holes Ul9n-2 and Ul9n-3 failed to perform. In one case, these failures were due to the excessive grout temperature, and in the other cases it was due to VCO damage caused by Accelerometer No. 2 at the device horizon in U19n-2 recorded an acceleration Fig. 12). This corresponds to an approxi-mate velocity of 0.11 m/sec (0.35 ft/sec). The VCO of vertical accelerometer No. 1 in U19n-3b had a negative band edge (i.e., was affected by electromagnetic phenomena), but it recorded a positive signal at 71.4 msec, indicating a peak accelerometers located at a depth of 610 m in Ul9n-3 recorded signals at 152 msec. In addition, two of the accelerometer signals were integrated by amplifiers within the instrument package. These signals are shown in Fig. 13.

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Horizontal accelerometer No. 3 140-msec delay Vertical accelerometer No. 50.2 V/cm Vertical accelerometer No. 6 Downhole integration of accelerometer No. 4 Downhole integration of accelerometer No. 6 Fig. 13. Oscilloscope traces of acceleration signals (including two integrations) at a radius of 403 m (station 3c in satellite hole Ul9n-3).

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Table VII. Summary of subsurface acceleration and velocity information. Ul9n-1 Velocity gage Vertical 22.30 No signal Velocity gage Horizontal 22.35 No signal bElectronically integrated within the transducer package. cDisplacement is toward the working point. dDisplacement is vertically upward. Table VII summarizes all of the measured subsurface acceleration and velocity information. This includes sigShock-Front Time of Arrival The two slifers in Ul9n performed in spite of the electromagnetic-current surges that originated in …