The San Diego/Tijuana Earthquake Scenario

 

At 7:31AM on May 16th 2017, a Magnitude 7.0 Earthquake occurred along the Rose Canyon Fault off of San Diego at location 32.850°N, 117.258°W at a depth of 4.9 km.

Only it didn’t, it was just a scenario, prepared by the USGS with the Earthquake Engineering Research Institute to help develop plans for risk reduction in the Tijuana/San Diego region. This region is home to more than 5 million people, with interconnected and interdependent economies and infrastructures.  The scenario, and others like it, help answer questions like:

  • How prepared is the region in the case of a major earthquake?
  • What types of damages and impacts can be expected and perhaps more important, what types of impacts may be unexpected?
  • What will the social and economic impacts be to the region?
  • And what can be done now to improve earthquake safety and resilience?

This is a volunteer effort, involving architects, geologists, seismologists, emergency managers, planners, building officials, and even social scientists and economists. They are working in three interconnected teams to help put together an integrated view of the event and what might happen and how best to respond:

  1. Earth Science – What is likely to happen when the fault slips?
  2. Engineering – How are structures designed and how will they respond?
  3. Social Science – What are the impacts on the social systems and economics of the region?

Multiple partners, working together, will prepare recommendation on how to improve resilience and recovery.

Priority Recommendations from the PEER Study on the South Napa Earthquake

 

The M 6.0 South Napa Earthquake of August 24, 2014, was the first earthquake to strike a major metropolitan area in the State of California in over two decades. During that quiescent period, the State’s population grew significantly, thousands of new businesses were started and thousands of new buildings were built. This means that the 2014 South Napa quake has provided an opportunity to learn about how we plan for, build for, and respond to earthquakes, as well as educate millions of Californians who are ‘new’ to earthquakes about them.

In October 2014, the Seismic Safety Commission held a public hearing in American Canyon, California, to better understand impacts and lessons learned from the South Napa earthquake. The Commission engaged its longtime partner, the Pacific Earthquake Engineering Research Center based at UC Berkeley, to research and report on the impacts and lessons learned from the earthquake.

The 55 page report contains 12 “Priority Recommendations,” which are important for anyone living or working in California. The majority is in the ”structures” category, since improvements in our built environment has perhaps the most direct positive impact on safety and recovery. These are presented below and organized under the same headings as the report.

  1. Geosciences
    • Identify the locations of complex and integrated fault zones in the state, like the West Napa Fault Zone, and prioritize these for evaluation and mapping and potential designation as Alquist-Priolo Earthquake Fault Zones.
    • Evaluate the effects of current amendments and exemptions under the Alquist-Priolo Earthquake Fault Zone Act and accompanying regulations, and study ways to better regulate and fund geologic investigations and structural mitigation in Alquist-Priolo Earthquake Fault Zones.
  2. Infrastructure
    • Ensure that all State-required gas safety plans address the mitigation of system risks to seismic hazards.
    • Convene a State task force that includes local water and wastewater providers as well as fire departments across the state to identify vulnerabilities, mitigation options, and financial mechanisms to enhance the seismic resilience of local water and wastewater systems, particularly in areas vulnerable to widespread ground failure and that lack alternative water supplies for firefighting.
  3. Structures
    • Work with FEMA, the California Building Officials, and other professional engineering and architectural organizations to: ensure that curricula for training and certification of safety assessors are effective and more widely implemented, particularly for local government personnel; improve protocols for deploying and compensating safety assessors; expand the use of Building Occupancy Resumption Programs; and grant safety assessment authority to the Division of the State Architect for public K-14 schools and State-owned buildings.
    • Work with the California Building Officials and professional engineering and architectural organizations, including the American Institute of Architects California Chapter and Structural Engineers Association of California, to develop guidance for local jurisdictions on effective coordination and management of post- earthquake safety assessment processes.
    • Develop guidance and training for local fire departments and building owners and operators on alternative procedures to safely turn off damaged sprinkler systems following earthquakes.
    • Evaluate and enhance, as needed, training and inspection materials for school districts and staff to seismically secure non-structural systems, equipment, contents and furnishings in public and private schools.
  4. People and Businesses
    • Establish a State task force to consider the risks posed to the state by the large proportion of uninsured residents and businesses in high-seismic hazard areas, and identify options for improving the take-up, affordability, and terms of earthquake insurance coverage for California residents and businesses, as well as alternative earthquake recovery funding sources for both residents and businesses.
    • Evaluate and enhance, as needed, penalties and other consumer protections against post-disaster scamming by contractors and cost inflation.
  5. Government and Institutions
    • Strengthen seismic performance standards and contingency planning for all State and local correctional facilities.
    • Review and revise, as needed, State regulations guiding the transfer and housing of inmates in county jails during times of emergency.

Key Findings from the PEER Report on the 2014 South Napa Earthquake

 

The M 6.0 South Napa Earthquake of August 24, 2014 took the lives of two people, injured 300 others, and caused moderate to severe damage to more than 2,000 structures. The Commission engaged the Pacific Earthquake Engineering Research Center (PEER) to research the impacts and lessons learned from the quake and prepare a comprehensive report.

The report is organized around the areas of Geosciences, Infrastructure, Buildings, People and Businesses, and Government and Institutions.

The full report is 55 pages with great research and detail.  In a later Post we will cover the recommendations, here we provide some of the key findings:

  1. Geosciences
  • Afterslip (slippage on the fault after the principal earthquake) on the West Napa fault produced further damage and necessitated regional-scale on-going monitoring.
  • The S earthquake identified some critical gaps in mapping coverage and guidance that affected the abilities of city, county, and State agencies to identify and map hazard zones.
  1. Infrastructure
  • Investments in instrumentation, earthquake alerting systems, and advance remote sensing techniques plus the activation of the California Earthquake Clearinghouse all were valuable in assisting damage assessment and emergency response.
  • The earthquake demonstrated the long-term benefits of the State’s $12 billion highway bridge earthquake strengthening program.
  • The earthquake highlighted the vulnerability of natural gas transmission and distributions systems to earthquake-related ground failure.
  • The earthquake highlighted the vulnerability of water and wastewater systems to earthquakes, plus the hazards that earthquake-related water-system failures can pose.
  1. Structures
  • The earthquake helped to identify important gaps in building safety evaluations and procedures to barricade unsafe areas.
  • The City of Napa’s program to seismically retrofit unreinforced masonry buildings was successful in reducing damage and the risk to life safety posed by these buildings.
  • While modern buildings generally met or exceeded code performance standards in the Mw6.0 earthquake, damage to non-structural components was the greatest contributor to property losses.
  • There was generally good performance across a range of wood-frame residential construction vintages and styles. The vast majority of damage was caused by two well-known seismic deficiencies: unbraced chimneys and cripple walls foundations.
  • The significant damage to manufactured housing in the 2014 South Napa earthquake was almost exclusively associated with support systems rather than the homes themselves.
  1. People and Businesses
  • Deaths and injuries sustained in the earthquake point to continuing gaps in public awareness and education on earthquake safety and preparedness.
  • The earthquake highlighted gaps in earthquake insurance coverage for both homeowners and businesses.
  • The delay of the federal Individual Assistance program hindered recovery.
  1. Government and Institutions
  • The state’s Standardized Emergency Management System (SEMS) was effective in mobilizing a multi-jurisdictional, multi-level emergency response but significant areas for improvement and training have been identified.
  • The earthquake identified problems with the damage assessment and declaration processes and financing of local government post-disaster assistance.
  • The earthquake highlighted significant gaps in contingency planning at many key government and critical facility operations.
  • More pre-disaster planning and training for post-disaster recovery is needed at both the State and local levels.

Major earthquakes can cause damage and loss, but California has a history of studying and learning from earthquake to make our State safer for residents and businesses.  The Commission supported study by PEER is the most recent example of such efforts.

Building Codes Use Lessons Learned to Make Structures Safer

 

Buildings are complex. Foundation, walls, floors, roof, electrical, plumbing heating, cooling, insulation systems all come together through plans and labor to create a building. Understanding how such a system will perform under seismic stress (earthquake) is complex and hard to predict with precision. Good engineers and designers following standards can reduce loss when buildings shake, but not all earthquakes are the same and can vary in intensity, duration and the kind of shaking. Even the nature of the land underneath a building can make a major difference in impact. So when a major earthquake strikes, it is a living experiment, and there are always lessons to be learned. The 1971 San Fernando, 1989 Loma Prieta and 1994 Northridge earthquakes were costly in terms of lives and money, but we learned much about how to make things safer.

When freeways in California were built, engineers used the best practices of the day. But those three California quakes demonstrated that these were not adequate to withstand the impact of strong shaking. The vulnerabilities exposed by those quakes taught us valuable lessons, and since 1971 California has spent over $13 billion retrofitting thousands of freeway overpasses and bridges. In Los Angeles alone almost 850 were upgraded. This makes us safer on the road and reduces the costs of recovering from future seismic events.

Similar improvements have been made in building standards and codes, often driven by losses resulting from some natural or manmade disaster. Perhaps the first building code was the Code of Hammurabi (1800 B.C.), essentially a criminal statute that included capital punishment for shoddy workmanship. And major fires in history, including those in Rome, London, and Chicago have all led to the creation of new codes. Building codes have likewise been improved following storms and earthquakes. After hurricane Andrew in 1992, Florida instituted a statewide building code. And California has upgraded its code recommendations after major earthquakes.

Building to Code Makes a Difference When an Earthquake Strikes

Benefits of Building Codes

In the past 20 years, our understanding of how structures and materials respond to seismic events has grown tremendously. At the same time, building technologies have improved significantly in terms of efficiency. This means that new codes can save lives and save money.

As an example, Mike Chaney, Commissioner of the Mississippi Insurance Department, cited the impact of two major quakes in 2010, one in Chile and the other in Haiti. Although the Chile earthquake was much stronger (magnitude 8.8 compared with Haiti’s 7.0 earthquake) and both were felt in population centers, there were 521 casualties in Chile, but over 200,000 in Haiti. The Commissioner felt that stronger and enforced building codes were a major determinant of the difference.

An interesting story in Time Magazine in 2010 expands on this perspective. In it, John Mutter a seismologist and disaster expert at Columbia University’s Earth Institute notes, “Earthquakes don’t kill people, bad buildings kill them.”

 

 

Build to Code !

Some of the Economics of Building Codes

Adopting new materials and technologies reduce water and energy usage, and over the life of the building can save many times the initial costs of adopting them; in other words, modern codes are a good investment. State-of-the art building codes are opposed by many, especially builders, because they can increase the initial cost of a building. But they are good investments for owners, communities, and society as a whole.

The benefits of new building standards can be delayed by slow adoption of new codes and poor enforcement of codes by communities. This was another lesson learned from the recent Mexico earthquakes. There were good codes in place, but they were not uniformly enforced and many of the buildings that failed were not up to code. Money was saved in their construction, and lives were lost.