Hazard Assessment

Preparedness

Mitigation

Response

Recovery

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Rick Wilson, California Geological Survey Hong Kie Thio, AECOM

Tim McCrink, California Geological Survey Laurie Johnson, Laurie Johnson Consulting

Kevin Miller, California Office of Emergency Services Michael Hornick and Ed Curtis, FEMA Region IX

Coordinated with the partners below, and with other states through the National Tsunami Hazard Mitigation Program

Application of Probabilistic Tsunami Hazard Maps in California

Partners =

Los Angeles Crescent City

California has its faults!

Community and Maritime Mitigation

Harbor Improvement Reports and other products that integrate risk reduction methods for coastal hazards (tsunami, SLR, storm, etc.) into Local Hazard Mitigation Plans

Community and Maritime Recovery

Guidance for harbors, communities, and state to produce recovery plans for large local- (Cascadia) and distant-source events.

Land-Use and Construction

Single-set of Probabilistic Tsunami Hazard Analysis maps/products for multiple applications, including CA Seismic Hazard Zones, FEMA-RiskMap/FIRM, CA Building Code, and other uses

Tsunami Hazard Products for Land-Use/Construction, Mitigation, and Recovery Planning - Potential Use in National Guidance

Supported through Multi-Year Cooperative Technical Partnership with FEMA Region IX

Model of potential debris movement in Port of Los Angeles during large Alaska tsunami, for mitigation and recovery planning

March 2014: Rebuild in “tsunami resistant” Crescent City Harbor

› Seismic Hazard Mapping Act (SHMA) of 1990 › Hazard maps to “assist cities and counties in fulfilling their

responsibilities for protecting the public health and safety;” tsunami mapping added in 1991, but no additional funding

› Development of Zones of Required Investigation which cover:

› Multi-home (+4) or moderate to high occupancy development;

› Single structures with >50% improvement to the structure;

› Real estate disclosure of tsunami hazard

› Land-use planning for communities (Local Coastal Plans, Local Hazard Mitigation Plans, etc.)

› Formation of Work Groups (2012-2014) › California PTHA Work Group – results/improvements:

› “Community PTHA model” in CA viable scientifically

› Sources – make consistent with National Seismic Hazard Map, especially Cascadia Subduction Zone

› Modeling – improve DEM resolution (10m) and numerical model used

› Preliminary list of applications for products

› California Tsunami Policy Work Group › 47 recommendations

› Focus on mitigation and land-use, esp. SHMA

Work of CA-PTHA Work Group summarized in CGS Special Report 237 at www.tsunami.ca.gov

California Tsunami Policy Work Group report available at

WSSPC.org

Production and Uses of Probabilistic Tsunami Hazard Analysis Products

Our concept: Produce single set of risk maps/products for multiple uses

Probabilistic Tsunami Hazard Analysis Methodology

› Identification and setup (sub-fault partitioning of earthquake sources)

› Computation of fundamental Green’s function for sub-faults

› Definition of earthquake recurrence model – Use NSHM where appropriate

› Generation of large set of scenario events that represent source characteristics; use of logic-tree approach

› Computation of near-shore probabilistic wave-height exceedance

› Identification of dominant sources through source dis-aggregation

› Computation of probabilistic inundation hazard by computing disaggregated sources and comparing offshore wave-height

› Verification of modeling results in office and the field

› Produce maps and related products

Similarities between probabilistic seismic and tsunami hazard approaches

Offshore probability of exceedance for 975yr ARP

Disaggregation of tsunami hazard at Crescent City for 475yr ARP

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1. Finalize PTHA products A. Modeling for six different risk levels B. Review model results C. Transfer model results to maps D. Review and finalize second PTHA

report

2. Form Panels for: A. PTHA product review B. PTHA product application C. PTHA product legislative

3. Determine appropriate risk level and products for use A. 100 and 475yr Average Return Period (ARP) = FEMA RiskMAP B. 475 or 975yr ARP = Seismic Hazard Mapping Program C. 2475yr ARP = CA Building Code D. Others uses: land use/Local Coastal Plans, updating 2009

evacuation maps/planning, and risk analysis (HAZUS)

4. For State Seismic Hazard Mapping Program: A. Determine areas where “life-safety” is issue; Can communities

evacuate before tsunami arrival? B. Determine if SHMA/PRC needs strengthening C. Create CGS Special Publication 117-type documentation

SECOND GENERATION Model Results, AECOM for CGS (2015), Probabilistic Tsunami Hazard Analysis in Humboldt Bay; blue line is 2009 state inundation map line

Single-Set of PTHA Maps for Multiple Uses Process of Completion and Determining Use (2013-present)

The following buildings and other structures located within the Tsunami Design Zone shall be designed for the effects of Maximum Considered Tsunami (2475yr ARP equivalent) including hydrostatic and hydrodynamic forces, waterborne debris accumulation and impact loads, subsidence, and scour effects in accordance with this Chapter:

A. Tsunami Risk Category IV buildings and structures (e.g., hospitals and emergency shelters, emergency operations centers, first responder facilities, air traffic control, toxic material storage, etc.)

B. Tsunami Risk Category III buildings and structures (e.g., Public assembly halls, arenas, high occupancy educational facilities, public utility facilities, etc.) with inundation depth at any point greater than 3 feet, and

C. Where required by a state or locally adopted building code statute to include design for tsunami effects, Tsunami Risk Category II buildings (e.g., Office buildings, condominiums, hotels, etc.) with mean height above grade plane greater than the height designated in the statute, and having inundation depth at any point greater than 3 feet.

Exception: Tsunami Risk Category II single-story buildings of any height without mezzanines or any occupiable roof level, and not having any critical equipment or systems need not be designed for the tsunami loads and effects specified in this Chapter.

ASCE 7-16 and the CA Building Code 2018-2020 Building Code Updates for CA, OR, WA, HI, and AK

Slide information from ASCE Subcommittee chair: Gary Chock

Risk level (in years ARP)

Annual rate of

exceedance

Liveable/ Mitigated Operational Immediate

Occupancy Life Safety Collapse Prevention

100 50% in 50yr FEMA RiskMap/FIRM (Building Risk Cat. IV)

(Building Risk Cat. III)

(Building Risk Cat. II)

200 25% in 50yr DWR Flood Maps (for flood plains of Central

Valley)

475 10% in 50yr Seismic Hazard

Mapping Act (?) and FEMA RiskMap/FIRM

975 5% in 50yr Seismic Hazard Mapping Act (?)

2475 2% in 50yr Vertical

Evacuation Buildings

Building Risk Cat. IV

Building Risk Cat. III and

possibly Cat. II*

3000 1.67% in 50yr

EXAMPLE – Initial Performance-Based Approach - Preliminary risk levels for different applications (construction and land-use related)

*Instead of requiring Risk Category II structures and individual homes under a higher risk level (2475yr ARP), a lower risk level or multi-level approach can be used, where building performance requirements are scalable to different risk levels.

0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

475-year ARP

Balboa Island/Peninsula, Newport Beach

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0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

975-year ARP

Balboa Island/Peninsula, Newport Beach

0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

2475-year ARP

Balboa Island/Peninsula, Newport Beach

0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

2475-year ARP

Balboa Island/Peninsula, Newport Beach

0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

2475-year ARP

Balboa Island/Peninsula, Newport Beach

0.00 0.15 0.30 0.45 0.60 0.75

Kilometers

2475-year ARP

Balboa Island/Peninsula, Newport Beach

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Tsunami Travel Time • NOAA maps (example) • Scenarios/PACIFEX • State modeling • + 10 minute accuracy

Alaska-Aleutians 4-6 hrs

Cascadia 10m to 2hr

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Tsunami Evacuation/Clearance Time From draft pub by Nate Wood, USGS

We are working with USGS to develop tsunami evacuation/clearance times

statewide.

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PTHA Project Schedule and Planning • Present-2017: Development of Tsunami

Hazard Panels for planning/review/ implementation of PTHA products (What is focus? Who should be on each panel? When decisions needed?)

• PTHA product review • PTHA application • PTHA legislation

• PTHA maps, products (table below), and 2nd PTHA process report should be finalized in early 2017.

• USGS will likely complete work on state-wide evacuation modeling by mid-2017.

• Develop and assist pilot communities for use of PTHA products now to mid-2017.

• Begin to apply use of PTHA statewide in late 2017.

Questions?

Rick Wilson, CGS

Rick.Wilson@conservation.ca.gov

www.tsunami.ca.gov

916-327-0981