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Experts Warn: California Unprepared for Supershear Earthquake Threat

Experts Warn: California Unprepared for Supershear Earthquake Threat

USC and Statewide California Earthquake Center researchers warn that California faces a major hazard from fast-moving supershear earthquakes—events that produce shock fronts and could cause catastrophic damage under current building codes.

A collapsed section of a Southern California freeway illustrates potential earthquake damage, visually conveying the destructive power of major seismic events.

Source:

SciTechDaily

Scientists Sound Alarm on Supershear Earthquake Risk

Researchers at USC Dornsife College and the Statewide California Earthquake Center (SCEC) are raising urgent concerns about the risk of supershear earthquakes in California.

What Is a Supershear Earthquake?

Supershear earthquakes rupture so quickly along faults that they outpace their own shear (S) waves, similar to how a plane breaking the sound barrier causes a sonic boom. This creates shock fronts in the ground, resulting in exceptionally fierce and focused shaking. These events differ from typical earthquakes by channeling more energy along the fault, causing broader and more severe damage.

Scientific studies indicate about one in three major strike-slip earthquakes worldwide are supershear events.

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Artistic representation of seismic activity beneath the earth's surface, showing a glowing red energy burst indicative of an earthquake epicenter.

Source:

SciTechDaily

California’s Unique Vulnerability

Critical Faults at Risk

California’s San Andreas Fault and other strike-slip fault lines can generate magnitude 7 or higher earthquakes. The risk is not higher than in other regions, but the consequences are dire due to population density and infrastructure that is ill-prepared for this rare but devastating rupture mode.

  • Building Codes: Current California building standards are designed for standard quakes, not the directional, concentrated energy of supershear events.

  • Monitoring: Experts call for more seismic sensors and real-time analysis tools near major faults to detect and study supershear ruptures as they happen.

  • Public Awareness: Most residents are unfamiliar with the double-wave impacts that supershear quakes can deliver.

For an overview of earthquake preparedness in California, see the Earthquake Country Alliance.

A high-resolution visual from a seismic study simulation, presenting geological fault lines and earthquake scenarios relevant to California risk analysis.

Source:

USC Dornsife - University of Southern California

Urgent Steps and Scientific Recommendations

Expert Actions Needed

  1. Update building codes to require resiliency against the unique forces of supershear earthquakes, especially along known faults.

  2. Deploy denser and more advanced real-time seismic monitoring across the state’s fault systems.

  3. Engage government, industry, and academia in preparing for this underappreciated but very real threat.

Quote: "Preparation is not a matter of if, but when," researchers emphasize in their latest recommendations (USC Dornsife News).

Supershear vs. Typical Earthquakes

Feature

Typical

Supershear

Rupture Speed

Slower than S-waves

Faster than S-waves

Shaking Intensity

Localized

Stronger, extends farther

Damage Pattern

Perpendicular

Along fault line

Building Code Coverage

Partial

Not fully considered

Urgent Steps and Scientific Recommendations

Expert Actions Needed

  1. Update building codes to require resiliency against the unique forces of supershear earthquakes, especially along known faults.

  2. Deploy denser and more advanced real-time seismic monitoring across the state’s fault systems.

  3. Engage government, industry, and academia in preparing for this underappreciated but very real threat.

Quote: "Preparation is not a matter of if, but when," researchers emphasize in their latest recommendations (USC Dornsife News).

Supershear vs. Typical Earthquakes

Feature

Typical

Supershear

Rupture Speed

Slower than S-waves

Faster than S-waves

Shaking Intensity

Localized

Stronger, extends farther

Damage Pattern

Perpendicular

Along fault line

Building Code Coverage

Partial

Not fully considered

How often do supershear earthquakes occur globally?

About one in three major strike-slip earthquakes globally are classified as supershear events.

How often do supershear earthquakes occur globally?

About one in three major strike-slip earthquakes globally are classified as supershear events.

How often do supershear earthquakes occur globally?

About one in three major strike-slip earthquakes globally are classified as supershear events.

What are the main differences between supershear earthquakes and regular earthquakes?

What are the main differences between supershear earthquakes and regular earthquakes?

What are the main differences between supershear earthquakes and regular earthquakes?

How can California improve its building codes to account for supershear earthquakes?

How can California improve its building codes to account for supershear earthquakes?

How can California improve its building codes to account for supershear earthquakes?

What specific faults in California are most at risk for supershear earthquakes?

What specific faults in California are most at risk for supershear earthquakes?

What specific faults in California are most at risk for supershear earthquakes?

How do scientists monitor for supershear earthquakes?

How do scientists monitor for supershear earthquakes?

How do scientists monitor for supershear earthquakes?

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