Seismic engineering program report, May-August 1978

PREFACE

This Seismic Engineering Program Report is an informal document primarily intended to keep the ever-growing community of strong-motion data users apprised of the availability of data recovered by the Seismic Engineering Branch of the U.S. Geological Survey. The Seismic Engineering Program of strong-motion instrumentation is supported by the National Science Foundation (Grant CA-II4) in cooperation with numerous Federal, State, and local agencies and organizations.

This issue contains a summary of the accelerograms recovered from the National Strong-Motion Network during the period May I through August 31, 1978. Reports on the Sendai, Japan earthquake of June 12, the northern Greece earthquake of June 20, and the Santa Barbara, California earthquake of August 13 are included, along with abstracts of recent reports, notes on strong-motion information sources and the availability of digitized data, and other information pertinent to the U.S. Strong-Motion Program. The data summary presented in table I includes those accelerograms recovered (although not necessarily recorded) during the period May through August 1978; this procedure will be continued in future issues so that the dissemination of strong-motion data may be as expeditious and current as practicable. The Santa Barbara earthquake of August 13, 1978:

A reconnaissance report ----------------- Strong-motion results from the Santa Barbara, California earthquake of August 13, 1978 -------------- Abstracts of recent reports ----------------- Strong-motion information, data reports, and availability of digitized data ---------------------

Figure I - Location map for Japan earthquake of June 12, 1978 - - 2 - Location map for Greece earthquake of June 20, 1978 - 3 - Thessaloniki accelerogram from Greece earthquake - - - 4 - Location map, Santa Barbara earthquake of August 13, 1978 -------__------__ 5 - Accelerograms from Santa Barbara Courthouse and Cachuma Dam, Santa Barbara earthquake --------

RECENT STRONG-MOTION RECORDS

by R. L. Parcel la

Forty-one accelerograms were recovered from the cooperative National Strong-Motion Network during the period May l-August 31, 1978 (see table I, end of report). Records were also obtained from earthquakes near Sendai, Japan on June 12 and in northern Greece on June 20 (see the following preliminary reports).

Small earthquakes (magnitude 3.2-4.3) in the Imperial Valley produced several strong-motion records at the Brawley airport site and at four sites in the El Centro array; the array contains 13 accelerograph sites at 3- to 4-km spacings transverse to the 1940 earthquake surface rupture. Twenty-five strong-motion stations are currently installed in the Imperial Valley, including a six-story building instrumented with a nine-channel remote recording system. This network is the result of the cooperative efforts of the U.S. Geological Survey (USGS), the California Division of Mines and Geology (CDMG), and the California Institute of Technology and was designed to fulfill such specific research needs as source-mechanism and ground-motion attenuation studies. Since January 1975, nearly 200 records have been recovered from this network; although the data obtained to date are of minimal engineering significance, the accelerograms do contain seismologic information useful in magnitude and epicenter determinations, wave propagation, and source-mechanism studies of the Imperial Valley region.

Twenty-one earthquakes were recorded between February and November 1978 at Monticello Dam in north-central South Carolina (see table I); the dam and reservoir are part of the Virgil C. Summer nuclear power facility operated by the South Carolina Electric and Gas Company (SCEG) and are located approximately 4 km northwest of Jenkinsville, S.C. The reservoir covers an area of about 2750 hectares and has an average depth of about 25 m. Filling of the reservoir began in late December 1977 and was accompanied by an abrupt increase in seismic activity (up to 100 events per day) recorded by a network of four seismographs operated by SCEG (Bob Whorton, oral commun., October 1978). Prior to filling of the reservoir, the USGS seismograph station at Jenkinsville had recorded one event about every 6 days. This increase in activity tapered off and then resumed abruptly in August 1978. Two strong-motion accelerographs were installed by the USGS in February 1978 as a result of the first increase in seismic activity. One accelerograph was placed in a steel-frame office building (45 m x 24 m) a few hundred meters west of the power plant; the other instrument was installed in a small plywood shelter (1.5 m x 1.5 m) on the south abutment of the largest of four embankment sections. The "abutment" instrument was removed in May 1978 and was replaced with the "office" instrument. Thirteen records with peak accelerations greater than 0.05 £ have been recovered from these two stations (table I). The largest acceleration was recorded at the abutment site and suggests a 0.253 £ peak horizontal ground acceleration in the "south" direction; the duration of strong-motion (greater than O.I g_) is about 0.06 s at approximately 25 Hz. This record has been attributed to a magnitude 2.7 event (depth 1.5 km) on August 27, 1978 at 1023:08 UTC (Pradeep Talwani, written commun., October 23, 1978) and contains the largest known recorded acceleration from an earthquake in central or eastern North America. Epicentre I distance is about I km. The absence of trigger minus S or S-P intervals on any of the 21 records indicates sources very near the recording stations.

Two strong-motion records were recovered from the CDMG Halls Valley station after a series of small earthquakes occurred on May II along the Calaveras fault about 15 km northeast of San Jose, Calif. The four largest events occurred at 0456, 0457, 0518, and 0528 local time and were assigned magnitudes of 3.1, 3.8, 3.7, and 3.1, respectively (Roy Miller, oral commun., September 1978). The accelerograms have been attributed to the magnitude 3.7 and 3.8 earthquakes and contain peak accelerations less than 0.05 £.

The Santa Barbara earthquake of August 13, 1554 (local time) produced three strong-motion records at USGS stations, one at a Southern California Edison station, and at least four at CDMG stations (table I). An assessment of earthquake damage and a summary of strong-motion data are contained in the following preliminary reports. Copies of the CDMG accelerograms were not available at this printing, although preliminary acceleration and duration data from four CDMG stations are included in table I.

BRIEF REPORT ON THE JAPAN EARTHQUAKE OF JUNE 12, 1978

by A. Gerald Brady

An earthquake with Richter magnitude 7.4 occurred at 1714 (local time) on June 12, 1978 off the coast of Japan's Miyagi Prefecture. The following report contains an assessment of the earthquake and its effects. Numerical values and statements not clearly the author's observations await confirmation by both subsequent investigation teams and official Japanese reports.

Two reports are in preparation in the United States, one published by Earthquake Engineering Research Institute (EERI, P. Yanev, ed.) and the other by National Bureau of Standards (NBS, B. Ellingwood, ed.); these reports are based on observations made by teams of investigators who visited Japan for various periods between June 19 and July 5, 1978. The team members represented the following institutions: the U.S.-Japan Cooperative Program in Natural resources (UJNR), the U.S. Geological Survey (USGS), EERI, NBS, the Federal Highways Administration (FHWA), the Federal Disaster Assistance Administration (FDAA), and URS/J.A. Blume and Associates.

The main earthquake was preceded by a smaller shock (magnitude not available) at 1703 and by a magnitude 6.8 shock on February 20, 1978 in the same general area. The June 12 earthquake was located at 38.15° N. and 142.22° E. at a depth of 30 km. The nearest strong-motion record was recovered at an epicentral distance of 70 km. The city of Sendai (pop. 600,000), where there are several instrumented buildings, is located at an epicentra I distance of 140 km. The intensity of shaking reached V on the JMA scale over an area of about 180 km by 60 km; strongest shaking was in the areas of Ofunato, Sendai, Shinjyo, and Fukushima. JMA V corresponds to MM I VII and VI I I and is partially described as "Very Strong - cracks in walls, overturning of gravestones, stone lanterns, etc., damage to chimneys and mud-and-plaster warehouses."

Figure I shows the northern part of the island of Honshu. The accelerograph sites at ground level (or in the basements or at first floors of buildings) are indicated, together with the peak accelerations in two horizontal directions and the vertical direction. Also included in the figure are two idealized isoseismal curves surrounding the JMA 5 and 4 intensity areas; the curves were constructed from JMA intensities recorded throughout Japan. Table 2 lists the peak accelerations at a number of sites, including the upper stories of buildings. The total number of records, out to epicentra I distances of almost 600 km, were collected from 90 stations, many of which had multiple instrumentation.

The record with the closest epicentra I distance, about 80 km, is the Kaihoku Bridge record (fig. I) with an acceleration of 0.3 £. Seismicity studies of aftershock data indicate an error in the location of the epicenter and that the main shock rupture plane, with a shallow dip to the west, actually reached a point about 70 km from the instrument, or within 30 km measured in plan. The record from an instrument located at the top of one of the bridge piers was off scale, at greater than 0.5 £ The instrumented high-rise buildings in Sendai exhibited no obvious structural damage although several minor cases of architectural damage were apparent. These included broken windows, upset shelves, and loosened veneers of brick and tile.

Digitization and preliminary corrections for all significant records are expected to be carried out by the Japanese agencies responsible for the instruments (see table 2).

Acknowledgment. The author would like to thank all those representatives from participating agencies in both the U.S. and Japan whose efforts resulted in the success of the visit by members of the several teams, and especially Mr. M. Ohashi, his guide.

Reference:

National Research Center for Disaster Prevention, Science and Technology Agency, Japan (July, 1978) "Prompt Report on Strong-Motion Accelerograms No. 15, June 12, 1978 Miyagi-Ken-Oki Earthquake."

Figure I.- Northern Honshu locations of ground level or basement accelerograph sites providing significant recordings, with peak accelerations in cm/s2 (2 horizontal, I vertical), and isoseismals for JMA 5 and 4 (JMA 5 approximates MMI VII and VIM).

PRELIMINARY REPORT ON THE NORTHERN GREECE EARTHQUAKE OF JUNE 20, 1978*.

A destructive earthquake occurred in northern Greece at 2303 (local time) on June 20, 1978 approximately 30 km northeast of the port city of Thessaloniki (Salonica). World-wide data recorded by the U.S. Geological Survey indicate that the shock had a magnitude of 6.4 (mt>) and was located at 40.82° N. and 23.15° E. at a depth of 16 km (fig. 2).

The earthquake caused an estimated 50 deaths and substantial localized damage in Thessaloniki and a number of smaller towns and villages in the most strongly shaken area, the Langadha-Volvi Lakes valley located 20 to 30 km east of Thessaloniki. More than 100 buildings constructed with unreinforced masonry materials were shaken down, although the most significant collapse was an eight-story reinforced concrete building in Thessaloniki, where 38 deaths occurred. The Greek government estimated the total damage caused by the earthquake was $190 million; the fraction of this damage that Sta. No. Owner* Location Structure

TH030 TH903 TH009 THOI8 TH028 THOI4 TH029 TH020 THOI3 TH006 THOI9 THO 1 6- 1 TH02 1 - 1 -2 THO 15 TH032 KTOOI

Organization responsible for collecting the original record and reporting accelerations: BRI - Building Research Institute RTRI - Railway Technical Research Institute PHRI - Port and Harbor Research Institute PWRI - Public Works Research Institute JAERI - Japan Atomic Energy Research Institute Instrument location: B-basement, GL-ground, F-floor, AB-abutment

Table 2.- List of strong-motion accelerograms

Sumi tomo do do BRI do do RTRI PHRI do do do do do do PWRI do do do do JAERI Sendai do do do do Miyako Sendai Shiogama Miyako Hachi none Aomori 1 waki Akita Of unato-Bochi Ishinomaki 1 waki do Akita 1 wate 1 baraki Sumi tomo Bldg.

do do Tohoku Univ.

do Atago School Sendai Office Shiogama Off ice Miyako Office Hachi nohe Office Aomori Office Onahama Office Harbor Office Breakwater Kaihoku Bridge Taira Bridge do Yuhei Bridge Masaki-Ohashi Br. Tokai resulted from the actual destruction of property is unknown.

Ground effects observed in the Langadha-Volvi Lakes valley include minor slope failure, sand boils associated with slumping and subsidence, and two zones of faulting, one extending northwest through the center of the valley and the second one trending approximately east-west along the southern margin of the valley (fig. 2). Although tectonic faulting at depth is clearly indicated, the surface rupturing and displacement may represent a combination of both primary and secondary effects. Surface expression of faulting through the center of the valley (total length about 10 km) indicates I eft-lateral strike-slip motion, probably not exceeding 2 cm. The rupture zone near the southern margin of the valley, approximately 8 km long, shows chiefly vertical offset with a maximum displacement of 30 cm.

This report summarizes some of the observations of the USGS investigation team consisting of R. P. Maley, C. G. Bufe, and R. F. Yerkes that spent seven days in the ep[centra I area after the earthquake. Inst. loc.*

1 13 Figure 2.- Location map showing rupture zones for northern Greece earthquake of June 20, 1978.

GENERAL EFFECT ON THESSALONIKI

A series of strong foreshocks began approximately 33 hours before the main shock; thus, a considerable part of the Thessaloniki population had already evacuated their residences when the major earthquake occurred. Many others left the city immediately, causing severe traffic congestion and numerous serious accidents. Some of the remaining population began to erect "tent cities" in any available space, particularly in the parks. In response to this actjon, the Greek army distributed 60,000 large tents to residents and prepared adequate sanitary facilities at the sites of large tent concentrations. Because of continuing aftershocks and the fear of an even stronger earthquake, only a limited number of residents had elected to return to their homes by late July, despite the fact that many of them lived in structures that had been inspected and were considered safe for occupancy.

After the earthquake, 100 two-man inspection teams were sent into the field to assess the relative safety of a I I buildings in Thessaloniki. These teams then posted the entrances with large colored stickers indicating the condition of occupancy: green, the structure was safe and could be used for normal living or business purposes; yellow, the building required repairs and could not be occupied although residents could temporarily re-enter to gather up their belongings; and red, entry was prohibited until the structure had been repaired. By July 7, 30,000 dwellings had been inspected and 9 percent of these received red stickers. The yellow- and red-stickered buildings caused considerable hardships particularly for businesses and building owners. One of the serious problems for Greek authorities involved the accommodation of 40,000 Thessalonians in new or temporary housing until reconstruction of the damaged housing could be completed.

Two strong-motion accelerographs were triggered by the earthquake, one in Thessaloniki 30 km from the epicenter and 20 to 30 km from the fault zone, and the second in Gevgelija, Yugoslavia, 80 km northwest of the epicenter. The Thessaloniki instrument, operated by the National Observatory of Athens, was installed in the basement of an eight-story building located on relatively poor alluvial soil a few hundred meters from the Gulf of Thessaloniki. A tracing of the record provided by J. Drakopoulos shows a maximum acceleration of 0.15 £, with each component recording 4 to 5 peak amplitudes exceeding 0.10 £ for intervals of from 0.6 to 1.2 s (fig. 3). The maximum acceleration recorded at Gevgelija was 0.04 £ (IZIIS, 1978).

The Thessaloniki instrument was triggered by several aftershocks that produced minor accelerations, except for the O.I2-g_ maximum acceleration recorded during the magnitude 5.0 July 4 aftershock.

Shortly after the June 20 earthquake, an investigation team from the Institute of Earthquake Engineering and Engineering Seismology, Skopje, Yugoslavia, installed three accelerographs in Greece: one at Skolari in the epicentral region and two in Thessaloniki, one on rock and the other near the collapsed eight-story building. Aftershock results from this network are not yet available.

Damage effects from the earthquake were concentrated in Thessaloniki, the largest city in northern Greece (population estimated at one million), as well as in a number of small villages situated in the Langadha-Volvi Lakes valley. Although numerous unreinforced masonry structures collapsed, particularly in the villages, the casualty toll was not large, owing to the occurrence of foreshocks the day before the earthquake. As a consequence, most people had evacuated their residences and were on open ground at eleven in the evening when the earthquake struck. Had this forewarning not occurred, many more casualties could have resulted because of building failures and fallen parapets (overhangs and facades) that were shaken loose on hundreds of buildings in Thessaloni ki.

Significant structural damage was limited to a few buildings in Thessaloniki, most notably the collapse of an eight-story reinforced concrete building that caused the majority of the fatalities during the earthquake. The remains of the structure had been demolished in the search for survivors before the USGS investigation team arrived. During the Figure 3.- Tracing of accelerogram from basement of eight-story building in Thessaloniki at epicentral distance of about 30 km; Greece earthquake of June 20, 1978.

collapse, the building, or part of it, apparently fell against an adjoining building, tearing out a section of the exterior waI I and knocking down several balconies. A second eight-story reinforced concrete building, located two and a half blocks from the collapse site, had badly damaged first-floor columns. Engineers from the Minsitry of Public Works (MPW) reported that the soil conditions in this area are unusual and that some of the present structures are situated partly on old brick ruins that have sunk well below the present ground surface. Presumably the area was brought up to grade by landfill many years ago.

NonstructuraI damage, though widespread throughout Thessaloniki, the older, more ornate external damage consisted cornices and overhangs, plaster spall ing from hollow-tile walls, fallen ornamental brickwork, marble facades that separated and dropped off walls, and spa I I ing between adjacent buildings that were constructed with no seismic separation. In one instance, decorative hollow concrete blocks used as a facade for an exterior stairway collapsed both inward on the stair side and outward onto the street and sidewaIk.

In the epicentral area the fault zone passed direct Iy through Skolari, ruptured a concrete slab in a garage, cut through the main road in town, and extended beneath a house that was damaged but did not collapse. Numerous unreinforced mud-brick and concrete-block farm buildings collapsed entirely, and some residences sustained badly cracked tile walls and could not be safely occupied. A large part of the damage in Skolari was clearly related to the existence of faulting under or near bu iId i ngs.

Ground rupturing in Yerakarou severely damaged a number of buildings, most notably several residential structures in the fault zone. The second floor of one two-story house was severely damaged; both exterior walls were near collapse and interior hollow-tile walls had toppled onto the bed, couch, table, and .2 150C WAVE ARRIVAL

TRIGGER ON P WAVE .2

4^J\j\jM\rfs<^/^^ ~ "

was concentrated in bu iIdings. Typical of fa I I en parapets , floor. Fortunately, the building had been evacuated when the foreshocks occurred (with the exception of the mother-in-law who survived the earthquake by sleeping on the ground floor).

Faulting was observed across the highway northwest of Stivos and within 10 to 20 m of a two-story reinforced concrete building under construction for the office and residence of a FINA service station. The most heavily damaged (west) side of the structure has no walls between ground level and the second-floor level, whereas the solid east wall of the building was undamaged except for the base of one corner column. The station operator reported that ground rupture occurred curing a large earthquake in 1932, but in a different location than the 1978 shock.

On the hill just above Peristerona a few stretches of linear fissures several hundred meters long appear to be a secondary faulting phenomenon, such as slumping or sliding. In contrast to other areas, the damage pattern in this village seems to bear no relation to the location of the fracture zone. The structures in the upper part of Peristerona are essentially intact, but at the base of the hill, just above the slope intersection with the highway, a number of houses and the entrance to a church were severely damaged. Several unreinforced concrete-block farm buildings in the valley northwest of Peristerona were flattened.

The USGS investigation team gratefully acknowledges the assistance of Minister M. Martis of northern Greece, Professors A. G. Galanopoulos and J. Drakopoulos of the National Observatory of Athens, Professor P. Carydis of the National Technical University of Athens, Professors B. C. Papazachos and G. Leventakis of the University of Thessaloniki, L. Semakis and Col. D. Beech of the U. S. Embassy in Athens, and members of the U. S. Consulate in Thessaloniki, Consulate General D. Zachary, Director of the American Center C. R. Sherak, and Nicos Papaconstininou who acted as i nterpreter.

Reference: IZIIS, 1978, Records of the KhaI Kiel iki earthquakes in the period May 23-June 21, 1978 obtained at IZIIS seismographic station: Institute of Earthquake Engineering and Engineering Seismology, University "Kiril and Metodij", Skopje, Yugoslavia, Report IZIIS 78-48, 19 p.

THE SANTA BARBARA EARTHQUAKE

A magnitude 5.1 (M 0 earthquake occurred off the coast of Santa Barbara, California on August 13, 1978 at 2254:52.4 UTC (California Institute of Technology). The earthquake had a focal depth of about 12 km and was located at 34.37° N. and 119.72° W. in the Santa Barbara Channel (W. Lee, oral commun., August 1978, fig. 4). Earthquakes in this area have not caused any known fault rupture on land since 1912; however, there have been two earthquakes in the Santa Barbara Channel, a magnitude 6.3 in 1925 and a magnitude 6.0 in 1941.

According to press releases, general damage included fallen items from grocery and liquor store shelves, broken windows, and mobile homes knocked off their supports. Conversations with fire officials revealed that there were some broken gas mains, possibly some earthquakerelated fires, and a potential tragedy that was avoided when an Amtrak passenger train was late coming to the area; a Southern Pacific freight train was derailed but damage was minimal (not observed by the author). No fatalities were reported; however, press releases indicate total damages of about $12 million.

Most of the damage occurred in the Go I eta area and included some of the buildings at the University of California campus. One such building, North Hall, is instrumented with a CRA-I 9-channel remote-recording accelerograph system owned by the Cat i fomia Strong-Motion Instrumentation Program (CSMIP). North Hall is a rectangular-in-plan three-story reinforced concrete structure. Damage to North Hall was minor and consisted of hairline cracking in the interior north-south shear walls, with most cracks oriented at an angle of about 45°. These hairline cracks occurred at all three floors and were more extensive on the first floor. No evidence of soi I-structure interaction was observed.

Other damage at the University occurred in the eight-story library building when thousands of books fell from shelves. No noticeable pattern of direction of fall was observed; however, most of the books came from the upper shelves, more falling at the upper two floors. Damage of the cover plates for seismic joints at floors one through four indicated relative

OF AUGUST 13, 1978: A RECONNAISSANCE REPORT

by B. L. SiIverstein

SANTA BARBARA CHANNEL

Figure 4.- Location map, Santa Barbara, California earthquake of August 13, 1978.

movement at these joints.

Structural damage to reinforced concrete overpasses occurred at the intersection of Highways 101 and 217. On one of these bridges, the fourth set of interior bents (from the southwest abutment) exhibited spa I led concrete and buckled reinforcing bar. At the southwest abutment the road decking is connected to the abutment support by steel rocker assemblies with 1-inch bolts. All but one of the upper bolts on the abutment side were sheared.

Damage in downtown Santa Barbara occurred when an unreinforced brick parapet fell outward and through the roof of an adjacent wood-framed bu iId i ng.

The Freitas Building in downtown Santa Barbara is also instrumented with a CSMIP-owned CRA-I. Completed in 1970, this rectangular-inplan building has four floors above and a halfbasement below ground level. An inspection of this building indicated no structural damage, but damage such as cracked walls, fallen objects, sheared and bent bolts securing air conditioning units at the roof level, and jammed doors suggests a strong east-west motion.

STRONG-MOTION RESULTS FROM THE SANTA BARBARA, CALIFORNIA EARTHQUAKE OF AUGUST 13, 1978

by R. L. Porcella, R. P. Maley, and A. V. Acosta

Eight accelerograms were recovered from strong-motion stations at Santa Barbara, Go I eta, Cachuma Dam, and the University of California, Santa Barbara campus (UCSB) in the days immediately following the August 13 earthquake. The main event occurred at 0354 in the afternoon (local time) and was assigned preliminary magnitudes (M [_) °f 5.1 (California Institute of Technology), 5.5 and 5.9 (University of California, Berkeley), and 5.5 (U.S. Geological Survey, Golden, Colo.). The hypocenter was located offshore about 6 km south of Santa Barbara at a depth of 10-15 km (W.H.K. Lee, C. E. Johnson, T. L. Henyey, and R. F. Yerkes, unpub. data, 1978).

Strong-motion instruments that triggered during the earthquake include triaxial accelerographs located at crest and toe sites at Cachuma Dam, a U.S. Bureau of Reclamation facility at an epicentra I distance of 34 km. A maximum horizontal ground acceleration of 0.12 £ (fig. 5) was recorded at the crest in a southwest direction, transverse to the axis of the embankment. A triaxial accelerograph installed at the basement level of the Santa Barbara Courthouse recorded a maximum horizontal ground acceleration of 0.21 g_ in the southwest direction (epicentral distance 6 km); the duration of strong-motion (greater than O.I £) was approximately 1.3 s. Additionally, this instrument recorded a small aftershock about 14 s after triggering during the main shock (fig. 5).

The Southern California Edison (SCE) company recovered a strong-motion record from an SCE power facility on Glen Annie Road in Goleta; the triaxial recording system (SMA-2) employs FM modulation on a four-track magnetic tape cassette. The analog readout indicates a peak horizontal ground acceleration of 0.28 £ (north direction). Epicentral distance is 19 km.

The California Division of Mines and Geology strong-motion instrumentation program (CSMIP) includes four sites in the Santa Barbara area that produced records during the August 13 event. Three of these sites are buildings instrumented by CSMIP in accordance with recently developed building instrumentation criteria. The record from a nine-channel system installed at the three-story North Hall building on the UCSB campus indicates peak horizontal accelerations of 0.44 £, 0.66 £, and 0.99 £ for the ground, third floor, and roof levels, respectively. Durations of strong (horizontal) motion (greater than O.I £) range from 2 s at the ground level to approximately 9 s at the roof level (table I). Epicentral distance is about 13 km.

The four-story Freitas Building in downtown Santa Barbara (epicentral distance 6 km) is instrumented with a nine-channel remote-recording system; the strong-motion record from the August 13 event shows peak horizontal accelerations of approximately 0.22 £, 0.30 £, and 0.67 £ at the basement, second floor, and roof levels, respectively. Durations of strong motion range from 0.5 s at the second floor to 7 s at the roof level.

The twelve-story Holiday Inn on Harbor Boulevard in Ventura is instrumented with a twelve-channel remote-recording system; accelerometers are located at ground, fourth floor, eighth floor, and roof levels. Maximum recorded acceleration is less than 0.05 £ at an epicentral distance of 40 km.

A CSMIP triaxial accelerograph at the Physical Plant station on the UCSB campus recorded a peak horizontal ground acceleration of about 0.37 £ in the south direction (epicentral distance 13 km). Duration of strong motion was approximately 1.5 s. Additionally, this instrument recorded a small aftershock about 17 s after triggering during the main event; maximum acceleration is less than 0.05 £ Two seismoscope records were recovered from USGS stations at the Santa Barbara Courthouse and the Bioscience building on the UCSB campus; maximum relative displacements recorded at these stations are 3.42 cm and 4.06 cm, respectively. Apparently, during the earthquake, a door fell on the seismoscope at the Bioscience building and may have affected the record.

The accelerographs that recorded the Santa Barbara earthquake were actuated during the early phases by vertically sensitive triggers that have a turn-on threshold of 0.01 £ over a frequency range of O.I to 10 Hz. Generally this threshold means that relatively near-field instruments are triggered by early P wave arrivals and, consequently, S wave minus trigger (S-t) time intervals (which approximate S-P times) may be scaled off the records. Previous studies have shown that when the ground motion is of an impulsive nature, triggering usually occurs within one- to twotenths of a second after the initial P-wave arrival. Thus, S-t times may be used to estimate the distance from an accelerograph to the source of a strong disturbance. Four instruments were located (in pairs) nearly equidistant from the Santa Barbara earthquake, two in Santa Barbara (Courthouse and Freitas Building) and two at the UCSB campus in Goleta (North Hall and Physical Plant). The S-t times on these records are approximately the same for the two UCSB stations, about 3 s, but vary by a factor of two for the Santa Barbara stations (table 3). Since the Santa Barbara sites are only a few hundred meters apart one may conclude that the Courthouse instrument, with a 340°

Figure 5.- Accelerograms from Santa Barbara courthouse and Cachuma Dam; Santa Barbara earthquake of August 13, 1978. Component direction refers to case acceleration for upward trace deflection.

S-t of 1.9 s, triggered normally, whereas the instrument at the Freitas Building, with a S-t of 0.9 s, triggered on later P-wave arrivals. Also, an aftershock was recorded at the UCSB Physical Plant and at the Santa Barbara Courthouse. Because the aftershock occurred during the instrument's operating cycle, the entire earthquake was recorded enabling the determination of true S-P intervals, 3.1 s at UCSB and 2.3 s at Santa Barbara. The S-P and S-t intervals at UCSB are nearly equal, whereas the S-P interval at Santa Barbara is about 0.4 s longer than the earlier S-t interval. This difference may be explained by a longer triggering delay (which seems unlikely considering the impulsive nature of the P-wave arrivals) or

CACHUAAA DAAA TOE

-.07g by a change in the source location of the aftershock relative to the main event.

The velocity model used by the California Institute of Technology Seismological Laboratory for locating earthquakes has P velocities of 5.5 km/s to a depth of 5.5 km and 6.3 km/s between 5.5 and 16.0 km depths (Kanamori and Hadley, 1975). Assuming a constant P to S wave ratio of 1.8, the respective S wave velocities would be 3.1 and 3.5 km/s. Using these values and a focal depth of about 12.5 km (W.H.K. Lee, C. E. Johnson, T. L. Henyey, and R.F. Yerkes, unpub. data, 1978) the aftershock records at Santa Barbara and UCSB indicate an epicenter located somewhat farther (5-6 km) from the strong-motion stations than has been determined from other recorded seismic data; these recalculated distance are II km for Santa Barbara and 19 km for UCSB. If the preceding assumptions are not too outrageous, we may suggest that the main shock rupture began at a location somewhat farther south or southeast of the location that teleseismic data indicate.

References: Kanamori, H. and Had ley, D., 1975, Crustal structure and temporal velocity change in southern California: Pure and Applied Geophysics, v, 113, p. 257-280.

ABSTRACTS OF RECENT REPORTS*

SEISMIC ENGINEERING DATA REPORT-- ROMANIAN AND GREEK RECORDS, 1972-77

by A. G. Brady, C. Rojahn, V. Perez, P. G. Carydis, and J. G. Sbokos

This report contains the results of digitizing and analyses of the Bucharest, Romania record of March 4, 1977, and of several strong-motion earthquake records recovered in Greece during the period from 1972 to 1975. The Bucharest record was provided by G. Serbanescu of the Building Research Institute (INCERC) in Bucharest, and the preliminary digitizing and analysis included here have been carried out by the U.S. Geological Survey. The section of the report on Greek records has been prepared by P. G. Carydis and J. G. Sbokos, of the National Technical University, Athens, Greece, who acknowledge the assistance in various ways of many of their co-workers.

The Geological Survey is publishing this report to bring these data to the attention of investigators throughout the world, but particularly to those in the United States. The analysis of the Bucharest record follows our standard techniques, which have been developed Table 3.- S-tri.gger and S-P -intervals from aeeelerographs near the sources

Station No.

5137 Freitas Bui Idi

5093 North Hal I - - - 13.1

885 Physical Plant - 13.2 of the Santa Barbara earthquakes

name distance (km) (s)

Courthouse - ing- 5.8 (C302)

(C2I3)

(C09I) Main event Main event epi central S-t

3.0 3. I 19

over recent years. It does represent, however, the first time that we have analyzed a record from a Japanese SMAC-B instrument, with 10-Hz natural frequency and critical damping. The digitizing and analyses of the Greek records represent an excellent addition to the data available for seismic engineering investigations. The processing is not identical to that used by the Earthquake Engineering Research Laboratory of the California Institute of Technology in their series of reports "Strong Motion Earthquake Accelerograms," nor to that used subsequently in the Seismic Engineering Data Reports of the U.S. Geological Survey, and we must stress that fact to prospective users. For example, a parabolic baseline has been fitted to the unconnected accelenation data. Those investigatons pnefenning a different fonm of long-peniod connection can nefen to the unconnected data as a stanting point; those data ane Iisted with the connected data.

Refenence: U.S. Geological Sunvey Open-file Repont 78-1022, 1978, 221 p.

This book nepnesents a joint effont by the Italian Commission fon Nuclean Enengy and the Italian State Powen Boand (CNEN-ENEL) and pnesents the nesults of vanious studies cannied out duning and immediately aften the Fnuili eanthquakes of May-June 1976. The book is divided into chaptens that noughly connespond to each line of neseanch by the special working gnoups established by the CNEN-ENEL joint commission. The chaptens contain infonmation

• Indus ion of stnong-mot ion infonmation sounces is intended as a senvice to oun neadens and does not constitute endonsement of these neponts by the U.S. Geological Sunvey. Calcu 1 ated Aftershock aftershock S-P epi central (s) distance (km)

CONTRIBUTION TO THE STUDY OF THE FRUILI EARTHQUAKE OF MAY 1976 about research on the relation between surface geology and seismogenetic tectonic structures, macroseismic aspects and seismologicaI and statistical considerations, processing and interpretation of strong-motion records, soil behavior, and earthquake damage and structural analyses.

Request copies from:

U.S. Nuclean ReguI atony Commission, Office of Nuclean Regulatony Reseanch, Division of Reacton Safety Reseanch

Seismic and geotechnical data have been compiled fon 37 accelenognaph stations in Califonnia in an attempt to venify subsunface conditions and thus pnovide additional infonmation fon new studies of both existing and futune stnong-motion neconds. Selected sites include Santa Banbana Counthouse, Fenndale, Cholame, El Centno, Taft, Hoi listen, Pasadena, and 30 southenn Califonnia stations in the centnal Los Angeles and nonthenn mountains negions. These neponts include infonmation about the accelenognaph station, seismicity of the site, soil boning logs made in the general vicinity of the site, and selected time histony plots and nesponse spectna cunves. Infonmation about these neponts is available from National Technical Information Service, Springfield, VA 22161.

STRONG-MOTION INFORMATION, DATA REPORTS, AND AVAILABILITY

U.S. STRONG-MOTION NETWORK DATA A Strong Motion Information Retrieval System (SMIRS) has been developed to provide up-todate information about strong motion records and the circumstances in which they were recorded to anyone having a computer data terminal. The system is operating, but the information within it is incomplete and needs to be verified. A user's manual is available (Converse, 1978), and the system was described in the January - April Program Report (USGS,

The strong-motion records from the February 9, 1971 San Fernando, California earthquake and most of the significant records prior to that event have been digitized by the California Institute of Technology (Hudson, 1976). Processing and analysis of the data have been presented in a series of reports containing (I) uncorrected digital data, (2) corrected accelerations, velocities, and displacements, (3) response spectna, and (4) Founier amplitude spectra. AM of these data reports are available through the National Technical Information Service (NTIS).

The digitization and analysis of the significant records subsequent to the San Fernando earthquake have been carried out by the U. S. Geological Survey (USGS). Processing and analysis of this data is presented in a series of USGS open-file Reports. When published, these reports are available from the USGS, Open-File Services Section.

The digitized data from the CIT digitization program are available from the Environmental Data Service (EDS) and the National Information Service for Earthquake Engineering at the University of California, Berkeley (NISEE) in the fonms indicated below. The magnetic tape digital data fnom subsequent years will be available from EDS and NISEE at approximately the same time as the data reports are pub Iished.

CIT Volume II data (connected) and

USGS data (complete): EDS and

OF DIGITIZED DATA

Volume III data (response spectra) on tape: NISEE

NISEE data (unconnected) on EDS data on tape: EDS and For reports or data regarding strong-motion records and data, address inquiries to the appropriate agency listed below:

1. EDS/NOAA
2. NISEE/Computer Applications
3. Open-file Services Section
4. California Division of Mines
5. National Technical Information Service

References: Converse, A., (1978) Strong motion information retrieval system user's manual, USGS Open-file report 79-289, 51 p. Hudson, D. E. (1976), Strong motion earthquake accelerograms - index volume, Caltech, EERI report 76-02, 72 p.

Because of the long history of close cooperation between the U.S. and the central and south American strong-motion programs, much of the data from those programs are available from the same sources as the U.S. data (see above). Information about strong-motion data from the western hemisphere will be included in the Strong-Motion Information Retrieval System operated by the USGS. The USGS does not attempt to obtain first class copies of records from those foreign organizations which prepare data reports comparable to those prepared by the USGS. Abstracts of the data reports from such organizations are presented in this Seismic Engineering Program Report series, and through informal arrangements, copies of the data and records are made available. The Environmental Data Service of NOAA has attempted to obtain copies of digitized strong-motion data from all organizations world-wide. National Geophysical and Solar-Terrestrial Data Center Boulder, CO 80302

Davis Hal I, DC Berkeley Berkeley, CA 94720

Box 25425 Federal Center Denver, CO 80225

and Geology Office of Strong-motion Studies 281 I "0" Street Sacramento, CA 95816

U.S. Dept. of Commerce Springfield, VA 22151

Table I.- Summary of accelerograms recovered during May - August3 1978

25 March 1977 1544 UTC Imperial Val ley 32.97N, 115. SOW Magnitude 3.4

21 October 1977 0612 UTC Imperial Valley 32.90N, 115. SOW Magnitude 4.3

24 February 1978- 16 March 1978 Jenkinsvi 1 le, S.C. Epicenters and magnitudes unknown

16 March 1978- 3 May 1978 JenkinsviIle, S.C. Epicenters and magnitudes unknown

See footnotes at end of table. Station name (owner)

Brawley Airport Ground level (USGS)

Brawley Airport Ground level (USGS)

Jenkinsvi 1 le, S.C. Mont i eel lo Dam (USGS)

Abutment (Office)

Shared abutment (Center crest)

JenkinsviIle, S.C. Mont ice Ilo Dam (USGS)

Shared abutment (Center crest)

Note: One additional (questionable) event was recorded; maximum acceleration less than 0.05 g_. Station S-t2 Accl coord. (s) direction

32.99 N 1.8 315° 1 15.51 W Up

32.99 N 1 15.51 W

34.30 N 81 .33 W

34.30 N 81.33 W Max accl Duration

180° Up 090° 180° Up 090°

I80e Up 090° .02 .07

.15 l-peak .10 |-peak .07 .06 .06 .07 ##

.06 .04 .09 Table I.- Summary of accelerograms recovered during May - August3 1978 -Continued

20 March 1978- 31 May 1978 Imperia 1 Va 1 1 ey Epicenter and magnitude unknown

2 May 1978 0617 UTC (a) Imperial Va 1 ley 32.85N, II5.42W Magnitude 3.2

2 May 1978 0617 UTC (b) Imperial Val ley Epicenter and magnitude unknown

5 May 1978 0533 UTC Cent. Alaska 63.I4N, 150. 85W Magnitude 5.0

1 1 May 1978 1157 UTC San Jose, Ca. 37.38N, I2I.76W Magnitude 3.8

1 1 May 1978 1218 UTC San Jose, Ca. 37.37N, I2I.77W Magnitude 3.7

12 May 1978 1216 UTC Cent. Alaska

62. IN, 149. 2W

See footnotes at end of table. Stations-name (owner)

El Centro Array 2 Keystone Rd (USGS) El Centro Array 9 Commercial Ave (USGS)

El Centro Array 4 Anderson Rd (USGS) El Centro Array 6 Huston.Rd (CDMG) T

El Centro Array 4 Anderson Rd (USGS) El Centro Array 6 Huston.Rd (CDMG) T

Talkeetna, Alaska FAA-VOR (USGS)

Ha 1 1 s Va 1 1 ey Grant Ranch (CDMG)

Halls Val ley Grant Ranch (CDMG)

Talkeetna, Alaska FAA-VOR, (USGS) 2 45 Station S-t Accl Max accl Duration coord. (s) direction (g_) (s)

32.92 N - ** 1 15.37 W

32.79 N - ** 115.55 W

32.86 N - 230° 0.05 1 15.43 W Up .02 140° .05 32.84 N 2.7 ** 1 15.49 W

32.86 N 2.0* 230° .03 1 15.43 W Up .07 140° .05 32.84 N 2.8* ** 1 1 5 . 49 W

62.30 N - ** 150. 10 W

37.34 N 1 . 1 ** 121 .71 W

37.34 N - ** 121 .71 W

62.30 N - ** 150.10 W Table I.- Summary of accelerograms recovered during May - August, 1978 - Continued

4 June 1978 0357 UTC S. Cal ifornia 33.92N, II7.83W Magnitude 3.6

13 August 1978 2254 UTC Santa Barbara, Ca. 34.37N, II9.72W Magnitude 5.5

See footnotes at end of table. Station name Station S-t (owner) coord. (s) direction

Carbon Canyon Dam 33.91 N (ACOE) | 17.84 W Crest 1.8 R. Abutment 1 .8 Diemer Filter Plant 33.91 N (MWD) 1 17.82 W Admin. Bldg. 1.8 Reservoir 1 .8 Orange Co. Reservoir 33.94 N 2.0 (MWD) I 17.88 W

Cachuma Dam 34.59 N (USBR) 1 19.98 W Crest 2.1

Santa Barbara 34.424N 1.9 Courthouse basement II9.7I2W (USGS) U.C. Santa Barbara 34.422N 3.0 Physical Plant II9.85IW (CDMG) U.C. Santa Barbara 34.4I6N 3.0 North Hal 1 1 I9.846W (CDMG)

Ground floor (center)

Ground floor (center)

channel (2)

Ground floor (center)

channel (3)

Ground floor (end)

channel (4)

Third floor (center)

channel (5)

Third floor (center)

channel (6) Max accl Duration Accl (g_) (s)

340° 0.08 Up 250° 340° Up 250° 222° Up 132° 180° UP090°

.02 .12 l-peak .03 .02 .07 .21 1.3 .07 .10 l-peak .37 1.5 .14 l-peak .31 1.5

. 1 1 l-peak

.56 6 Table I.- Summary of accelerograms recovered during May - August, 1978 - Continued

Event Station name Station S-t Accl Max accl Duration

See footnotes at end of table. (owner) coord. (s) direction (c[) (s)

Roof level (center) 180° 0.99 9 channel (7) Third floor (west end) 360° .59 5 channel (8) Third floor (east end) 360° .66 5 channel (9) Santa Barbara 34.424N 0.9 Freitas bldg. II9.698W (CDMG)

Ventura, Calif. 34.276N - ** Holiday Inn II9.294W (CDMG)

Note: Building is 12 stories above ground level and is instrumented _ . .. . -

North Hall) and Goleta (Freitas Bldg.) are approximations.

with a 12-channei CRA-I remote recording system. Accelerometers are located at ground, 4th floor, 8th floor, and roof levels. A vertical starter is located at ground level; a horizontal starter is located at the roof level.

Table I.- Summary of accelerograms recovered during May - Augusts 1978 - Continued

27 August 1978 1023 UTC JenkinsviIle, S.C. 34.3IN, 81.33W Magnitude 2.7

3.1 August 1978- 6 November 1978 JenkinsviIle, S.C.

See footnotes at end of table. (owner)

Go 1 eta, Cal if Glen Annie Rd (SCE) Note: A small aftershock was recorded at U.C. Santa Barbara Physical

JenkinsviIle, S.C. Mont ice Ilo Dam (USGS) f Shared abutment (Center crest) Station

Plant and Santa Barbara Courthouse. Maximum acceleration less than 0.05 £. Two seismoscope records were recovered at UCSB and Santa Barbara Courthouse; maximum relative displacements are 4.06 and 3.42 cm, respectively. coord.

s-t2

direction (s)

2.4 Max accl Accl

090° 0.24 Up 360° Duration

.08 .04 .06 (s)

1.0 Table I.- Summary of accelerograms recovered during May - August3 1978 - Continued

o Event Station name Station S-t Accl (owner) coord. (s) direction

ACOE - U.S. Army Corps of Engineers CDMG - California Division of Mines and Geology MWD - Metropolitan Water District SCE - Southern California Edison USBR - U.S. Bureau of Reclamation USGS - U.S. Geological Survey t - WWVB time code is incomplete or nonexistent; correlation of accelerogram with event is questionable. S-wave minus trigger time. ^Denotes S-P interval, that is, the earthquake occurred within the instrumental run-time of a previous event. Azimuthal direction of case acceleration for upward trace deflection on accelerogram (opposite direction to pendulum motion). Case acceleration for vertical component indicated as up or down. Unless otherwise noted, maximum acceleration recorded at ground or basement level. ** denotes maximum acceleration is less than 0.05 g_ at ground stations or less than 0.10 g_ at upper floors of buildings. ~~ Duration for which peaks of acceleration exceed 0.10 g_. Max accl (g_)

180° 0.22 Up 090° 180° Up 090° Duration

l-peak .1 1 .16 .13 .17 .24 (s)

O.I 0.3 0.2 0.3

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