CEA research helps ensure sound rates
California Earthquake Authority (CEA) works hard to ensure that policyholders get earthquake insurance rates based on the best available science.
Our ongoing commitment to the following research projects helps inform our scientifically-based insurance rates. It also helps us better understand how to prepare for and reduce the damages caused by major earthquakes.
Why are these projects so significant?
- They will be used to create the next version of the National Seismic Hazard Maps for California.
- These maps shape all seismic design, so they will greatly influence future construction of nearly all buildings in California.
- Specifically for homeowners, these projects have helped quantify earthquake risk in California so they can make informed decisions on how to protect their household finances from the costs of recovering from earthquake damage.
CEA-PEER Cripple Wall project
The CEA–PEER project “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings” is a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research (PEER) Center and funded by the CEA.
Quantifying the difference of seismic performance of unretrofitted and retrofitted single-family wood-frame houses is important in California due to the high seismicity of the state. Inadequate lateral bracing of cripple walls and inadequate sill bolting have been observed to be primary reasons for damage to residential homes, even in moderate earthquakes.
The overall objective of the CEA–PEER project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies.
Within the CEA–PEER Project, detailed work was conducted by seven Working Groups, each addressing a particular area of study and expertise and collaborating with the other Working Groups. The seven Working Groups are as follows:
Working Group 1: Resources Review
Working Group 2: Index Buildings
Working Group 3: Ground Motion Selection and Loading Protocols
Working Group 4: Experimental Testing Program
Working Group 5: Analytical Modeling
Working Group 6: Interaction with Claims Adjustors and Catastrophe Modelers
Working Group 7: Reporting
The resulting project research demonstrated that a brace-and-bolt retrofit is significantly valuable and has a great cost-benefit ratio—namely that a retrofit could save potentially hundreds of thousands of dollars in damage repairs to a single-family wood-framed house after an earthquake.
CEA Damage-Assessment Guidelines
In 2007 CEA provided major funding for the Consortium of Universities for Research in Earthquake Engineering (CUREE), whose work produced the “Assessment and Repair of Earthquake Damage” The guidelines were last updated in 2010.
To ensure guidelines continuity, CEA contracted with Applied Technology Council (ATC) in May 2018 to update the existing CUREE Guidelines and to develop companion engineering guidelines (Damage Assessment and Repair Guidelines for Residential Wood-Frame Buildings. Vol. 1 – General, Vol. 2 – Engineering”).
The new guidelines are available for free download on the CEA website (Volume 1, Volume 2) and can be ordered through the ATC's online store. Volume 1 of the series is intended to be used by insurance claim representatives, building contractors, homeowners and others familiar with construction and repair, while Volume 2 is intended to be used by structural and geotechnical engineers and others with relevant technical experience.
The ATC 110 earthquake-guidelines-development project is now called FEMA P-1100, Vulnerability-Based Seismic Assessment and Retrofit of One- and Two-Family Dwellings.
A joint project of CEA and the Federal Emergency Management Agency (FEMA) makes it easier and less expensive to protect certain types of homes from earthquakes. The two-volume publication titled Vulnerability-Based Seismic Assessment and Retrofit of One- and Two-Family Dwellings is intended to reduce the time needed for design and permitting of seismic retrofits and increase the number of homes that remain livable after an earthquake.
Contractors, architects, engineers and skilled homeowners who are planning to retrofit certain types of at-risk residential structures can download them by clicking on the links below or order the free printed publication, consisting of a “prestandard” and several plan sets prepared by ATC, by calling (800) 480-2520.
- Volume 1 – Prestandard (PDF)
- Volume 2A – Plan set Crawlspace (PDF)
- Volume 2B – Plan set Living Space over Garage (PDF)
- Volume 2C – Plan set Chimney (PDF)
- Volume 3 – Background Documentation (PDF)
FEMA P-50 AND QUAKEGRADE®
FEMA P-50 was developed after the Northridge quake. This study has created a simple, standard assessment form to evaluate a house's resistance to earthquake damage based on:
- Structural attributes
- How close a house is to earthquake hazards
This assessment form helps homeowners identify how to strengthen their houses and lower their earthquake risk.
CEA also launched a web-based application based on FEMA P-50 for use by home inspectors. QuakeGrade® uses data the inspector inputs as they note certain structural and geological conditions of the house. From these data points, the application calculates a seismic-vulnerability score, which supports a report that describes the inspected house’s seismic vulnerabilities and identifies potential retrofit options—implementing the retrofit options can mitigate the vulnerabilities and improve the vulnerability score.
South Napa Study
CEA commissioned Dr. Sharyl Rabinovici to conduct a study that surveyed and analyzed what happened to single-family dwellings and homeowners in the 2014 South Napa M6.0 earthquake. The study consisted of an on-line survey, interviews, and home inspections. The Executive Summary (PDF) summarizes these findings.
The results show a population widely impacted by a moderate event, and individuals who are resourceful and resilient but faced with many challenges in handling earthquake vulnerabilities.
Insights gained about the beliefs and experiences of Napa homeowners can help CEA further improve its insurance offerings and mitigation programs, as well as advance state-of-the-art earthquake retrofit performance research.
Read the full CEA South Napa Study Report (PDF).
UCERF3 (Uniform California Earthquake Rupture Forecast)*
UCERF3 is a report that provides estimates of the magnitude, location and likelihood of earthquakes striking throughout the state.
According to UCERF3:
There is a more than 99 percent chance in the next 30 years one or more magnitude 6.7 or greater earthquakes will hit somewhere in California.
The research also reports that scientists now can consider more than 250,000 different fault-based earthquakes, whereas previous research and models considered far fewer.
The research reports that the likelihood of an earthquake of magnitude 8 or greater in the next 30 years in the entire California region has increased 50 percent over previous (UCERF2) estimates.
An even more powerful quake—a magnitude 7.5 or greater—has a 48 percent chance of striking California in the next 30 years.
There is a 75 percent chance that a magnitude 7 or greater earthquake will strike in Southern California sometime during the next 30 years.
In the next three decades, there's a 76 percent chance that a magnitude 7 or greater quake will happen in Northern California.
NGA-West2 (Next Generation Attenuation)*
NGA-West2 is a scientific study that advances research aimed at helping us more thoroughly understand the effects of earthquake ground motions. This information:
- Leads to the ongoing improvement of codes and retrofit guidelines
- Provides earthquake loss modelers one of the key inputs necessary to estimate damage to residential structures
- Combined with other CEA-sponsored research, is used to calculate insurance rates
- CEA has been honored by the Earthquake Engineering Research Institute for our innovative work with UCERF3 and NGA-West2.
- In 2014, CEA also received an award for excellence in educational outreach in mitigation, research and public education from the Western States Seismic Policy Council.
Questions about our research?
For more information about CEA research, contact:
(916) 661-5000 or firstname.lastname@example.org