December 22, 2003 San Simeon Earthquake Rakesh K. Goel, PhD, PE Professor, CE & ENVE Cal Poly, San Luis Obispo, CA Email: rgoel@calpoly.edu
Acknowledgement Sam Vigil, Cal Poly, SLO Post-earthquake reconnaissance and Photos Garret Hall, Cal Poly, SLO Khalid Mosalam, UC Berkeley Josh Marrow, SGH Lew Rosenberg, SLO County Geologist United State Geological Survey (USGS) California Integrated Seismic Network (CISN) The Tribune (San Luis Obispo, CA) R. K. Goel San Simeon Earthquake Slide No. 2
Outline Seismology Ground Motion Performance of Structures Paso Robles Atascadero Oceano San Luis Obispo Performance of Wineries R. K. Goel San Simeon Earthquake Slide No. 3
The Ground Shakes A moderate earthquake of Magnitude 6.5 strikes the Central Coast of California on December 22, 2003 at 11:15:56 AM local time 2 confirmed dead 40 injured in Paso Robles/Templeton area. 1 building collapsed and more than 40 severely damaged in Paso Robles Area Atascadero City Hall damaged and closed for operations. Estimated loss to be equivalent of $200 millions R. K. Goel San Simeon Earthquake Slide No. 4
Seismological Aspects R. K. Goel San Simeon Earthquake Slide No. 5
Magnitude of an Earthquake Local or Richter Scale, M L Based on measurements on a Wood-Anderson seismometer located 100 km from the epicenter Not appropriate for measuring large earthquakes Surface Wave Magnitude, M s Based on measurements of surface waves (Rayleigh) Best for measuring shallow earthquakes at large epicentral distance Moment Magnitude, M w Based on seismic moment that depends on the rock rupture strength, area of rupture, and amount of slip Considered to be best for measuring large earthquakes R. K. Goel San Simeon Earthquake Slide No. 6
Relationship Between Different Scales The Richter (or Local) scale saturates at about 7 The Surface Wave Magnitude saturates at about 8 The Moment Magnitude scale does not saturate Figure: Kramer, Prentice Hall, 1996 R. K. Goel San Simeon Earthquake Slide No. 7
Magnitude of the Earthquake Moment Magnitude of the San Simeon earthquake estimated by USGS: M w = 6.5 This magnitude is indicative of energy released by rupture of the fault Indicates damage potential in the epicenter region Does not mean that a region far from the epicenter, e.g., San Luis Obispo City, also experienced the same magnitude earthquake Intensity scale (e.g., Modified Mercalli Scale is more indicative of damage potential in different areas. R. K. Goel San Simeon Earthquake Slide No. 8
Intensity Scale: Modified Mercalli Scale Indicates how much shaking was felt in any location from same magnitude earthquake Scale from I to XII I = not Felt V = felt by everyone, objects overturned, no structural damage VII = considerable damage to poorly designed (e.g., unreinforced masonry) construction XII: total destruction Different intensity scale noted for different locations for the same earthquake R. K. Goel San Simeon Earthquake Slide No. 9
Intensity Scale for San Simeon Earthquake VII: Atascadero, Cambria, Cayucos, Los Osos, Morro Bay, Nipomo, Oceano, Paso Robles, San Miguel, San Simeon, and Templeton VI: at Arroyo Grande, Grover Beach, Guadalupe, Pismo Beach, San Luis Obispo, Santa Margarita and Santa Maria Information: USGS R. K. Goel San Simeon Earthquake Slide No. 10
Faults in central Coast Seismic hazard to central coast of California HosGri Fault Cambria Fault Oceanic Fault San Simeon Fault Rinconada Fault San Andreas Fault Information: USGS R. K. Goel San Simeon Earthquake Slide No. 11
San Simeon Earthquake Epicenter 11 km (6 miles) NE (49 ) from San Simeon 17 km (10 miles) N (356 ) from Cambria 20 km (13 miles) W (260 ) from Lake Nacimiento 39 km (24 miles) WNW (283 ) from Paso Robles Depth of 6.7 km (4.7 miles) Information: USGS R. K. Goel San Simeon Earthquake Slide No. 12
Epicenter The epicenter is the point on the earth's surface vertically above the hypocenter (or focus), point in the crust where a seismic rupture begins. Information: USGS R. K. Goel San Simeon Earthquake Slide No. 13
Fault at Fault Exact location is currently unknown but northern portion of Oceanic Fault is the likely candidate No surface rupture found Information: USGS R. K. Goel San Simeon Earthquake Slide No. 14
Prior Earthquake in Vicinity of San Simeon M5 to M6 (?) earthquake in 1853 M5.7 earthquake in 1906 M L 6.2 in 1952 Current earthquake of M w = 6.5 in 2003 Is there a pattern of significant event about every 50 year? R. K. Goel San Simeon Earthquake Slide No. 15
Fault Types Strike Slip Horizontal motion between two plates Normal Vertical motion with side above the incline sliding down Due to tension between two sides Reverse or Thrust Vertical motion with side above the incline sliding up Due to compression between two sides R. K. Goel San Simeon Earthquake Slide No. 16
Strike-Slip or Thrust Motion between Pacific-North American plate in California is primarily strike-slip A few compression zones also exist R. K. Goel San Simeon Earthquake Slide No. 17
San Simeon Earthquake The earthquake occurred on a thrust (or reverse) fault zone Thrust events build the coastal mountain ranges of central coast of California. http://www3.uakron.edu/geography/lrb/physf97/lectures/platetect/sld031.htm R. K. Goel San Simeon Earthquake Slide No. 18
Recorded Motions R. K. Goel San Simeon Earthquake Slide No. 19
Recorded Accelerations Station Name Station Network Dist. Horiz Apk (g) No./ID (km) Ground Struct. Cambria Hwy 1 Bridge 37737 CGS 13.179 - - San Antonio Dam 36258 CGS 22.12.22 Templeton 1-story Hospital 36695 CGS 38.483 1.28 Parkfield Vineyard Canyon 36441 CGS 49.09 - - Los Osos Point Buchon 36427 CGS 52.09 - - San Luis Obispo - Rec Ctr 01083 USGS 62.165 - - Information: CISN R. K. Goel San Simeon Earthquake Slide No. 20
Motions in San Luis Obispo Information: CISN R. K. Goel San Simeon Earthquake Slide No. 21
Motions in Templeton Information: CISN R. K. Goel San Simeon Earthquake Slide No. 22
Directivity Effects Motion in Templeton, which is 38 km from the epicenter, are larger than in Cambria, which is only 13 km from the epicenter? Peak horizontal ground accelerations are 0.48g in Templeton and 0.18g in Cambria Larger motion in Templeton is due to directivity effects Fault rupture started at the epicenter and progressed South-East towards Templeton Larger accelerations occur in the direction of fault rupture due to Doppler-Type effects R. K. Goel San Simeon Earthquake Slide No. 23
Comparison with Design Code Information: CISN R. K. Goel San Simeon Earthquake Slide No. 24
Structural Performance R. K. Goel San Simeon Earthquake Slide No. 25
Locations of Major Cities http://www.slocoupons.com/maps_1.htm R. K. Goel San Simeon Earthquake Slide No. 26
Structural Performance Overview Significant structural damage in Historic Downtown district of Paso Robles Significant nonstructural damage in Templeton and Atascadero Minor to moderate nonstructural/geotechnical damage in Oceano Minor nonstructural damage in San Luis Obispo R. K. Goel San Simeon Earthquake Slide No. 27
Damage in Paso Robles R. K. Goel San Simeon Earthquake Slide No. 28
Damage in Paso Robles Major damage in three blocks of historic downtown district of Paso Robles Bounded by 12 th and 13 th streets in eastwest direction, and Spring and Railroad Streets in the northsouth direction R. K. Goel San Simeon Earthquake Slide No. 29
Damage in Paso Robles Red-tagged buildings on 12 th street between Spring and Pine Streets Park Street between 12 th and 13 th Streets Yellow-tagged buildings on Other streets of the three-block area R. K. Goel San Simeon Earthquake Slide No. 30
Observations on Damage Pattern Unreinforced masonry buildings suffered the most damage Many such buildings are more than 100 years old Not designed for seismic loads Lack detailing to transfer seismic forces from structure to the foundation Unreinforced masonry buildings have been known to be seismically vulnerable State and local codes require retrofit but the deadline was 2008 to 2018 R. K. Goel San Simeon Earthquake Slide No. 31
Acorn Building Located in historic downtown Paso Robles Housed the landmark Clock Tower Two Story Unreinforced Masonry building Built in 1892 Photo: Paso Robles Chamber of Commerce R. K. Goel San Simeon Earthquake Slide No. 32
Acorn Building: After Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 33
Acorn Building Roof was not tied properly to the walls East-west motion of the roof imposed large deformations on the outer wall in second story Second story wall collapsed The roof slides to the side, bends over the first floor wall, and crushes cars and two victims Photo: The Tribune (1/24/03), SLO, CA R. K. Goel San Simeon Earthquake Slide No. 34
Acorn Building Photo: Rakesh Goel Photo: Rakesh Goel Photo: Josh Marrow R. K. Goel San Simeon Earthquake Slide No. 35
Marlow Interior Building Located on corner of 12 th and Park Street Large open windows on 12 th and Park Street sides of the building Solid walls with few openings on other two sides Photo: Josh Marrow R. K. Goel San Simeon Earthquake Slide No. 36
Marlow Interior Building Significant asymmetry in building plan Torsional motions during shaking Significant cracks in walls facing the street sides Large demands on these walls due to torsion Photo: Sam Vigil R. K. Goel San Simeon Earthquake Slide No. 37
Marlow Interior Building Photo: Sam Vigil Photo: Sam Vigil Photo: Sam Vigil R. K. Goel San Simeon Earthquake Slide No. 38
Bistro Laurent Building Located on corner of 12 th and Pine Streets One story unreinforced masonry building Retrofitted by tying roof diaphragm to the walls Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 39
Bistro Laurent Building: Retrofit Details Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 40
Bistro Laurent Building Only minor to moderate structural damage No cracks in the masonry walls Few bricks from the decorative parapet separated Building was only yellow tagged Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 41
Ali s Persian Rug Building Located on the corner of Park and 13 th Streets Formerly housed Bank of Italy Three-story unreinforced masonry building Built in 1918 Photo: Khalid Mosalam R. K. Goel San Simeon Earthquake Slide No. 42
Ali s Persian Rug Building Damage to unreinforced masonry façade and parapets No ties between façade and the main wall Bricks peeled due to outof-plane motion and stresses imposed on the joints due to drift Building red-tagged Photo: Khalid Mosalam R. K. Goel San Simeon Earthquake Slide No. 43
Ali s Persian Rug Building Photo: Sam Vigil Photo: Sam Vigil Photo: Sam Vigil R. K. Goel San Simeon Earthquake Slide No. 44
Ali s Persian Rug Building: Repair (1/18/04) Photo: Rakesh Goel Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 45
Rustic Ranch Furniture Gallery Unreinforced masonry building sandwiched between two other buildings No structural damage apparent except for broken window glass Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 46
Rustic Ranch Furniture Gallery Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 47
Paso Robles Inn Observation tower did not suffer damage Brick façade supported on space frame One of the unreinforced masonry building housing quest quarters was damaged Significant cracks in walls Moderate nonstructural damage Broken window glass Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 48
Paso Robles Inn Photo: Rakesh Goel Photo: Sam Vigil Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 49
Paso Robles Inn: Precaution Photo: Rakesh Goel On 12/23/03 Photo: Rakesh Goel On 1/18/04: Boarded-Up R. K. Goel San Simeon Earthquake Slide No. 50
Carnegie Library Photo: Rakesh Goel Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 51
City Hall Parking Lot: Rupture of Sulfur Springs Photo: Rakesh Goel Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 52
Sulfur Spring Photo: Rakesh Goel Photo: Rakesh Goel On 1/18/04 Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 53
Damage in Atascadero R. K. Goel San Simeon Earthquake Slide No. 54
Atascadero City Hall Reinforced concrete space frame Brick façade Built in 1918 by town founder E. G. Lewis Partially retrofitted Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 55
Atascadero City Hall Photo: Lew Rosenberg R. K. Goel San Simeon Earthquake Slide No. 56
Atascadero City Hall Brick façade peeled off the rotunda Moderate cracking in interior partition walls City Hall has been closed Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 57
Atascadero City Hall Retrofit prevented parapet collapse Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 58
Atascadero City Hall Hazard from falling bricks Photo: Rakesh Goel Photo: Sam Vigil R. K. Goel San Simeon Earthquake Slide No. 59
Atascadero City Hall Typical nonstructural damage Photo: Rakesh Goel Photo: Rakesh Goel R. K. Goel San Simeon Earthquake Slide No. 60
Typical Damage to Contents Photo: Rakesh Goel Photo: Sam Vigil R. K. Goel San Simeon Earthquake Slide No. 61
Damage in Oceano R. K. Goel San Simeon Earthquake Slide No. 62
Damage in Oceano Pavement damage at Oceano airport Sink holes and damage to tanks at Waste Water Treatment plant Damage to houses close to the beach Shifting off the foundation More than 30 water main break Street pavement damage R. K. Goel San Simeon Earthquake Slide No. 63
Damage in Oceano Damage typical of lateral spreading/ loose sandy soils Photo: Lew Rosenberg Pavement Damage Photo: Lew Rosenberg House Damage R. K. Goel San Simeon Earthquake Slide No. 64
San Luis Obispo R. K. Goel San Simeon Earthquake Slide No. 65
San Luis Obispo (SLO) More than 125 unreinforced-masonry buildings in downtown area About 25 have been seismically upgraded No significant structural damage reported Accelerations were about 17%g in SLO compared to perhaps more than 50%g in Paso Robles Performance of unreinforced-masonry buildings in SLO would not be significantly different than in Paso Robles if the shaking in SLO had been stronger R. K. Goel San Simeon Earthquake Slide No. 66
San Luis Obispo Photo: Rakesh Goel Historic Ah Louis Store survived with minor damage Photo: Rakesh Goel Mission San Luis Obispo de Tolosa came out with only a minor crack R. K. Goel San Simeon Earthquake Slide No. 67
Damage to Templeton Area Wineries R. K. Goel San Simeon Earthquake Slide No. 68
Damage to Wineries Wineries along Hwy 46 west of Templeton sustained heavy nonstructural damage damaged glasses and bottles of wine in tasting facilities broken bottles in the valuable wine libraries ruptured stainless steel wine tanks collapse of wine barrels stacked in pyramids and on portable steel racks rupture of wine barrels and loss of a substantial amount of wine R. K. Goel San Simeon Earthquake Slide No. 69
Damage to Wineries Photo:Josh Marrow Photo:Josh Marrow Photo:Josh Marrow R. K. Goel San Simeon Earthquake Slide No. 70
Damage to Wineries Photo:Josh Marrow Photo:Josh Marrow Photo:Josh Marrow R. K. Goel San Simeon Earthquake Slide No. 71
Conclusion and Lessons Unreinforced masonry (URM) buildings are highly susceptible to seismic loading Potential for collapse Significant hazard from falling bricks from façade Even basic seismic retrofit tying floor/roof diaphragm to walls minimized the collapse potential for URM building San Simeon earthquake tested several retrofitted buildings in Paso Robles Most retrofitted buildings survived without major damage R. K. Goel San Simeon Earthquake Slide No. 72
Conclusion and Lessons Buildings on street corners performed poorly Asymmetric in building plan due to large open windows on street sides Torsional motions impose larger demands on lateral load resisting elements during earthquake Buildings at the end of the block performed poorly compared to similar buildings in midblock End buildings gets kicked out by neighboring building Need special attention during retrofit R. K. Goel San Simeon Earthquake Slide No. 73