Structural Damage and Structural Damage and Response to Historic Response to Historic California TsunamisCalifornia Tsunamis

By Orville T. MagoonBy Orville T. MagoonCoastal Zone FoundationCoastal Zone Foundation

Seismic Safety Commission Seismic Safety Commission Workshop May 15, 2005Workshop May 15, 2005

April 1, 1946 TsunamiApril 1, 1946 TsunamiHalf Moon Bay, CaliforniaHalf Moon Bay, California

Crescent City

1974

High Water Mark High Water Mark

High Water Mark – 20.6’ High Water Mark – 20.6’ MLLWMLLW

1300-1700 Hrs

23 May 1960

0.0097 CPM Filter

Cresent City, CA

Tsunami Gate Okushiri, Japan

Top of Gate 11.7 m above low waterTop of Gate 11.7 m above low waterGate automatically closes after 4 Mag EarthquakeGate automatically closes after 4 Mag Earthquake

Research Research NeedsNeeds

• Historical ReviewHistorical Review

• Cascadia Subduction ZoneCascadia Subduction Zone

• Near Field EventsNear Field Events

• Coastal ResonanceCoastal Resonance

• Existing Engineering Model BasinsExisting Engineering Model Basins– Oregon State Tsunami BasinOregon State Tsunami Basin– Texas A&M Hydraulic LabTexas A&M Hydraulic Lab

Research Research NeedsNeeds

• Structural Engineering GuidanceStructural Engineering Guidance• Coastal InfrastructureCoastal Infrastructure• Prototype Reference Long Wave Prototype Reference Long Wave

Measurement Measurement (i.e. Cresent City, CA)(i.e. Cresent City, CA)• Economic and Environmental ImpactsEconomic and Environmental Impacts

• Vulnerability Maps• Vulnerability Research and EducationVulnerability Research and Education• Risk Management Assessment and Risk Management Assessment and

CommunicationCommunication