2010 chile earthquake ground motions

M8.8 Offshore Maule, CHILE Earthquake of 27 February 2010:27 February, 2010:

STRONG MOTION DATA & ISSUESby Mehmet Çelebi ESC USGS Menlo Park Caby Mehmet Çelebi, ESC, USGS, Menlo Park, Ca.

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OUTLINE

• ACKNOWLEDGEMENTS• INTRODUCTION & SCOPE &GENERAL• INTRODUCTION & SCOPE &GENERAL

MAPSFOCUS STRONG MOTION NETWORK• FOCUS:STRONG-MOTION NETWORK, MAIN-SHOCK, TEMP. ARRAYS (Strong-h ki d ti t d f ti )shaking duration, permanent deformation)

• DISCUSSION

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EVENT OVERVIEW• Saturday February 27 2010 at 06:34:14 UTC• Saturday, February 27, 2010 at 06:34:14 UTC• Known facts (Mw=8.8, Ml=8.8), Faulting Mechanism: Thrust faulting due to

subducting Nazca Plate beneath South America Plate, • Depth=35km Epicenter (35 909°S 72 733°W ]• Depth=35km, Epicenter (35.909 S, 72.733 W ]• Number of Dead (~500 out of which ~250 attributed due to tsunami) [down

from earlier reports of ~800 and up from 341]• ~ Approximately 1.5 M people displaced [Not too many tent cities]pp y p p p [ y ]• ~ 3,000 tall buildings (>10- stories) in Chile. ~ 80 damages and only 1

collapsed (Concepcion where 8 people were killed). [EERI:50 possibly to be demolished]. Current estimates of economic loss: ~$30B.

• 2 weeks after the main shock the country was running pretty well and Chilean• 2 weeks after the main shock, the country was running pretty well and Chilean people proved to be resilient once again as they experience earthquakes often.

• Rupture (Rupture length ~400-450 km).• Nearest towns: Cauquenes: 31362; Constitucion (38,000)q ( )• Affected poopulation Centers: Santiago(~6m), Vina/Valparaiso(~1.5m),

Concepcion and vicinity (~1.5m)• Scope of this talk is mainly engineering oriented – and mainly strong-motions

related

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related.

BEST RESOURCES: COLLEAGUES/FRIENDS

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Maps from NYT95 k (60 il ) NW f• 95 km (60 miles) NW of Chillan, Chile

• 105 km (65 miles) NNE of105 km (65 miles) NNE of Concepcion, Chile

• 115 km (70 miles) WSW of Talca, Chile

• 335 km (210 miles) SW of SANTIAGO, Chile

Affected Area :[500km x 60-100 km]

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From J. Gomberg: Rupture “area” and shake-maps??

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Intensity Zoning and Affected Populations

7From USGS

General Comments on Strong-MotionThere is no “National Strong Motion Network”g

• The 2 current networks are privately funded: – University of Chile: Approximately 60 groundUniversity of Chile: Approximately 60 ground

stations and 4 structures (2 bldgs and 2 bridges).[mixture of SMA, QDR and Etna]

– Catholic University of Chile(~10 of which 5 are in Santiago, 5 are in Northern Chile.[mixture of Chinese SMAC and few Etnas]Chinese, SMAC and few Etnas].

• ADDITIONAL-Seismology Dept of Univ of Chile (Santiago)Chile (Santiago)

• Temp Arrays (aftershocks): USGS + Univ of British Columbia

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British Columbia

General Comments on Strong-Motion• University of Chile: At the moment no government

support for operation. Approximately 60 ground stations and 4 structures (2 bldgs and 2stations and 4 structures (2 bldgs and 2 bridges).[mixture of SMA, QDR and Etna]. 2 technicians + faculty. Attempt to leverage for support from government (Data release pending!) Note: Mostfrom government (Data release pending!). Note: Most digital instruments were deployed to capture an expected rupture in the north half of ChileC th li U i it f Chil ( 10 f hi h 5 i• Catholic University of Chile(~10 of which 5 are in Santiago, 5 are in Northern Chile.[mixture of Chinese, SMAC and few Etnas]. No techs…faculty operating!

• 5 of 6 USGS K2’s are loaned to UNIV of Chile and are deployed as of 3/25/2010 at: Matanzas, Pichilemu, Constitucion, Couqenes, Talcahuano.

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Constitucion, Couqenes, Talcahuano.

General Comments on Strong-Motion• Very few stations have site characterization

information• Washington State University and GEER

have both agreed to conduct site characterization work (each for 3 stations)

• Univ of Chile requested USGS to help on this (conveyed to managers).

• As expected, recorded ground motions are affected by variation of site conditions in Santiago and elsewhere

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From: CHILE RESEARCH NEEDS WORKSHOP, WASH. D.C. (August 19, 2010) DRAFT REPORT dated October 21, 2010

• The 2010 Chile earthquake was a landmark event in which the largest earthquake ever recorded by scientific instruments affected a vast populated region containing natural, built, and social systems representative of those in region containing natural, built, and social systems representative of those in the United States. The event represents an enormous test bed on how earthquakes occur and how they affect technologically advanced societies, study of which can lead to rapid and vital advances in knowledge and

ti A f d h i d t t k ti l d t f thpractices. A focused research program is urged to take timely advantage of the science and engineering lessons of the 2010 Chile earthquake.

• This earthquake mechanism involved subduction of the Nazca plate beneath the South American plate over a 500 kilometer-long by 100 kilometer-widethe South American plate over a 500 kilometer long by 100 kilometer wide zone. The rupture, geological deformations, and earthquake ground motions therefore can be considered as a preview of what might happen when a similar large earthquake occurs on the Cascadia subduction zone of the Pacific N th t f th U it d St t t th t h t d i d dNorthwest of the United States, an event that has not occurred in recorded history but is anticipated. The opportunity to learn from the Chile earthquake, and to plan ahead for a great Cascadia earthquake, is unprecedented and fundamental to advancing seismic risk reduction in the Pacific Northwest.g

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SEISMICITY: On the average….M7 or larger earthquake every 15 years

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From: CHILE RESEARCH NEEDS WORKSHOP, WASH. D.C.(August 19, 2010) DRAFT REPORT dated October 21, 2010( g , ) ,

• This is the largest earthquake ever recorded by strong motion instruments. Therefore, rather than extrapolating to great earthquakes, or using numerical p g g q gsimulations for the same purpose, for the first time we can calibrate ground motion prediction models using actual recorded ground motions from a great earthquake. The recorded motions show very long duration and, in many cases peculiar frequency content Studying the attenuation of ground motionscases, peculiar frequency content. Studying the attenuation of ground motions with distance, the effects of local site conditions, and the effects of regional geology are critical needs for advancing ground motion simulation and prediction methodologies and for advancing the seismic design of buildings and other infrastructure.

• LEARNED DURING WORKSHOP THAT:– There are only 34 main-shock records (22 from CE Dept-Univ of Chile) +12 (Seismology Dept

+ others)+ others)– NEW NETWORK of 297 DIGITAL INSTRUMENT TO BE DEPLOYED IN THE NEAR

FUTURE– MAGNITUDE 7 EVERY 5 YEARS,– MAGNITUDE 4 OCCURRING 5 TIMES A WEEKMAGNITUDE 4 OCCURRING 5 TIMES A WEEK

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From: CHILE RESEARCH NEEDS WORKSHOP, WASH. D.C. (August 19 2010) DRAFT REPORT dated October 21 2010(August 19, 2010) DRAFT REPORT dated October 21, 2010

• PROPOSED RESEARCH ACTIVITIES RELATED TO S-M:– Size / Slip / Data from a subduction zone. For slips in range of 15-20 meters, such studies will answer questions

f i il i i ll i h U S h f d il blfor similar environments especially in the U.S. where very few data are available.– The impact of long-duration strong-shaking components of the records and effect on cyclic-responses of

structures in Chile as well as possible other locations where similar earthquakes are expected (e.g., Pacific Northwest of the United States).

– Vs30 issue and how the specific site classifications relying on Vs30 are not applicable in zones where site responses must include the area’s geometric and topographical formations in addition to deeper than 30 meter geotechnical environments typical of basins and other specific regions.

– Existing GMPE relationships and how they may be revised; How to better extrapolate ground motions in subduction zones in light of the data acquired in Chile.

– Building codes and design response spectra in Chile as well as the United States. It is important to follow up what “emergency revisions” to building codes are being proposed by post-earthquake established nine “emergency” code committees and how these may affect the revisions of building codes in the U.S.

– Specific site response issues (e.g., basin effects and how this issue should be treated in microzonation).– The reason why (a) high frequency content of the motions recorded during this earthquake as compared to prior

events, and (b) the specific velocity computations from strong-motions show maximum 65 centimeters/second for such a large magnitude earthquake. The “damage causing potential” effects of these characteristics need to be investigated.

– The post-event recovery of permanent displacements over time as documented by continuous GPS measurements particularly in Concepción offers opportunities to study for the first time such phenomenon where years of GPS data exist before the event also.

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STATUS OF ACTUAL DATA [TIME-SERIES] RELEASE

• SINCE FEBRUARY 27, 2010….VERY LIMITED DATA RELEASED.• THERE HAVE BEEN CONTINUOUS “SOON TO BE RELEASED…….”THERE HAVE BEEN CONTINUOUS SOON TO BE RELEASED…….

STATEMENTS• DURING THE AUGUST-WASH D.C.WORKSHOP, IT WAS MADE VERY

CLEAR TO THE CHILEAN COUNTERPARTS THAT THE OUTLINED/DESIRED RESEARCH PROJECTS CANNOT BE SUCCESSFUL WITHOUT THE DATA

• VARIOUS DIFFERENT STATEMENTS ARE MADE BY CHILEANSTh t th t i b i h h d th d t t b l d– That, the government is buying or has purchased the data….to be released

– That, once government provides funds for operation/maintenance of existing and new instruments, and for /processing/dissemination of retrieved data then the data will be releasedretrieved data…. then the data will be released.

• WE ARE ALL WAITING!!!!

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Summary table from: www.strongmotioncenter.org (as of 11-16-2010)

In general: velocities (max ~65cm/s) and intensities (max g ( ) (MMI=8) are low, but there is long-duration shakingNote: an additional record from Angol [Map] suggests 0.93g

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Released (Aug-2010):Summary Table from Univ. of Chile, CE Dept. :Angol: 0.93gConcepcion: 0.4gVi 0 33Vina: 0.33gValparaiso(rock); .27g, (soil)0.30gLlolleo: 0.56gSantiago: 0 36g & 0 56gSantiago: 0.36g & 0.56g

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Just Released:Summary Table fromU i f Chil CE D tUniv. of Chile, CE Dept. :Angol: 0.93gConcepcion: 0.4gVina: 0 33gVina: 0.33gValparaiso(rock); .27g, (soil)0.30gLlolleo: 0.56gLlolleo: 0.56gSantiago: 0.36g & 0.56g

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CONCEPCION• Many tall bldgs damaged

M f C i d d 7 t ll bld• Mayor of Concepcion decreed 7 tall bldgs to be demolished or owners to come up with

i l ithi 2 tha repair plan within 2 months• Edificio Alto Rio is the only one collapsed• New constructions have confinement

problems as well as vulnerability due to plan and vertical irregularities

• Several bridges in the vicinity damaged19

Seve a b dges t e v c ty da aged

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CCSPConcepcion-San Pedro(plots by Boroschek)

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Concepcion- City Center (plots by Boroschek): [Note 2 sec]p y (p y ) [ ]

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DURATION OF STRONG SHAKING:(Concern: Effect of “numerous” inelastic cycles on structures)

1999 IZMIT (Mw7.4) – duration~5 sec (YPT)

1985 CHILE(Ms7.8) – duration~>50s

2009 L’AQUILA (6.3) – duration ~ 7-8 sec

1940 EL CENTRO(Mw6.9)

2010 CHILE(Mw8.8) – duration~ >50 sec

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GPS DATA(courtesy of K. Larson)

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SANTIAGO

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SANTIAGO-GEOLOGY & SIGNIFICANT LOCATIONSLOCATIONS

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Maipu Geology: Pumicito (10-20m) over alluvium

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Maipu- strong motion station

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ENGINEERED STRUCTURES- SANTIAGO(next: Univ of Chile and Metro Mirador-site (

conditions different than Maipu: ~900 m deep cemented alluvium))

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Differentgeologygeologyaffected ground

Maipu Station

ground motions

Univ Chile Station

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METRO MIRADOR MAIPUUNIV CHILE

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Strong Motion Station Locations in Valparaiso & Vina del MarValparaiso & Vina del Mar

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Strong-motion stations instations in Valparaiso:

B h d dBoth recorded 1985

Above: church site(~56m thicksite(~56m thick alluvium over rock Right:rock, Right:

Rock (data not available yet)

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available yet)

Strong-motion station

in Vina delin Vina del Mar

1985 & 2010:Recorded peak at

0 33g34

~0.33g

2010 M8.8 Earthquake: Vina del Mar

From J. Wallace

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2010 M8.8 Earthquake- Vina del Mar & 1985 Vina del Mar (alluvium) and Valparaiso (USFM)[rock]

From J. Wallace

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VIEW OF PLOTS OF STATION :CCSP(CONCEPCION);www.strongmotioncenter.org[more on this later][more on this later]

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[Data USGS has]Preliminary USGSPreliminary USGS

Processing[Univ of Chile:[Univ. of Chile:

Seismology Dept][ALL: 100sps][ALL: 100sps]

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Data USGS Has: Peaks & meta-data problemsdata problems

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Temp: USGS-K2 Deployments as of 3/25/2010 [some data arrived]3/ 5/ 0 0 [so e d ved]

USGS K2 APPROX.Locations COORD.

Matanzas 33-57’38.55”S71-52’18 49”W71-52 18.49 W

Pichilemu 34-24’8.24”S72-0’33.64”W

Constitucion 35-20’4.86”S72-24’52.78”W

Cauquenes 35-56’18 78”SCauquenes 35 56 18.78 S72-194’6.33”W

Talcahuano 36-44’11.02”S

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73-6’16.948”W

Univ of Chile (Engineering stations+USGS temp) from Boroschek KMZtemp) from Boroschek KMZ

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Back to: Plots of data USGS has(plots by C D Stephens-These data will be(plots by C.D. Stephens These data will be

posted as “meta-data” is checked and i l d)processing completed)

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Preliminary Processing by C. D. Stephens

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Preliminary Processing by C. D. Stephens

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Preliminary Processing by C. D. Stephens

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Preliminary Processing by C. D. Stephens

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Preliminary Processing by C. D. Stephens

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THANK YOU!!THANK YOU!!

Q????Q????

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Temporary instrumentation by EERI team :Edificio Alvarez, Viña del Mar (16 Stories +3 bsmt), 2010 construction:

• Aftershock data: 3/27/2010 (M=4.9): 55km SSW of Valpaiso, (Analyses Continuing).

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• [Adopted from Digitexx Report]

Temporary instrumentation by EERI team

2 buildings in Santiago by NEES

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PermanentlyPermanently Instrumented

StructuresUNIV ofUNIV of CHILE

San Agustín Building Array

(Permanent) Building Response Observation (courtesy: E. Cruz)(Permanent) Building Response Observation (courtesy: E. Cruz)

San Agustín Building Array

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(Permanent) Base(Permanent) Base--isolated Building isolated Building R Ob ti ( t E C )R Ob ti ( t E C )

San Agustín Building Array

Response Observation (courtesy: E. Cruz)Response Observation (courtesy: E. Cruz)

San Agustín Building Arrayg g yFoundation Level 3 channels, U-D N-S E-W

g g yBase Level (Top of Isolation)3 channels as shown

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San Agustín Building Array

(Permanent) Building Response Observation (courtesy: E. Cruz) (Permanent) Building Response Observation (courtesy: E. Cruz)

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San Agustín Building ArrayIntermediate level (Second Floor)

San Agustín Building ArrayTop Level (Roof Slab)3 h l h3 channels as shown 3 channels as shown

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(Permanent) Clínica: Catholic Univ of Chile: Building Array

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C8

C9 C7

7

8

9

C6

C5

C4

4

5

7

6

2

3

4

C3

C2

C1

Agy1º S

2º S

1

Agx

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(Pemanent) Building Response Observation(Pemanent) Building Response Observation

C8

C9 C7 Clínica UC Building Array

Floor Response:

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8

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C6 C4 pSMAC-MD 3 channels per story(100 Hz.)

7

6

8 C6

C5

3

4

5

C3 C1

Foundation Level:SSA-1, 3 channels (200 Hz.)

Agy1º S

1

2 C2

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Agy1º S

2º SAgx