✓ Earthquake Forecasting, Prediction, and Early Warning

What is an earthquake forecast?

an estimate of the likelihood or probability that earthquakes of certain sizes will occur during specified periods of time

What goes into making an earthquake forecast?

• Geodesy (GPS Data): determining the rate at which tectonic stress is building up across major fault systems due to continuous motion of tectonic plates

• Geology and Paleoseismology: Fault Mapping (location of faults) and Past Earthquake Rates (the rate and magnitude of past earthquakes)

• Seismology: the occurrence patterns of past earthquakes

Ground shaking prediction maps

crucial tools used by seismologists and experts to quantify seismic hazard

Information a forecast does provide:

• Probability of Occurrence:

• Magnitude range and time interval

• Scientific Foundation (Geodesy, d. Geology/paleoseismology, fault slip and creep)

• Basis for seismic Hazard

Information a forecast does not provide:

• Exact Time or Date

• Specific Location (Epicenter)

• Ground Shaking Intensity

• Precursory Signals

Ways in which a forecast can change based on some other factors

the integration of new scientific data, improvements in how complex fault behavior is modeled, and updated estimates of a fault's readiness over time.

Can we predict earthquakes? Why or why not?

• No, we cannot make precise predictions of the date, time, and exact place due to :

  • Complexity of Fault

  • Behavior (Critical Failure Process)

  • Lack of Precursory Signals (No Silver Bullet)

  • Difficulty of Observation

What are the components needed for a useful seismic prediction?

• Interval of time

• Area of location

• Magnitude range

• Probability

What potential earthquake precursors have people identified? Explain why each of them is not reliable at all.

• Foreshocks/swarms - inconsistent

• Ground uplift and tilt - chaotic fault physics

• Radon and electrical conductivity - lack of successful testing

• Animal behavior

‘critical failure process’

• Constant Stress buildup: tectonic movements cause a constant and relentless build up of stress on existing fault plans

• Patch Failure: the continuous stress causes small parts of the fault -the individual "patches"- to fail and slip all the time

• The prediction problems: the key difficulty is that most of these slips remain small, but sometimes a small slip will unexpectedly propagate into a large, catastrophic rupture. Scientists currently lack the ability to predict which small failure will grow into a major earthquake

avalanche analogy

• the process of an earthquake rupture is often compared to an avalanche on a pile of sand

• The sand input (stress Buildup): a machine pours saint onto a pile at a a perfectly constant rate, representing the constant accumulation of tectonic stress

• The Failure (slip/avalanche): the sand piles up, the pile becomes to steep ands reaches a critical point where it collapses in an avalanche, representing the sudden release of stress in an earthquake

• The unpredictability: even though the input is constant, the timing, size, and location of each avalanche is chaotic and unpredictable.

earthquake early warning

system designed to detect the initial stages of an earthquake and rapidly transmit an alert ahead of the most damaging seismic waves

 J.D Cooper's original Earthquake Early Warning plan

developed in the wake of the 1868 Hayward Fault earthquake. His plan was based on the simple concept that seismic waves (which travel at the speed of sound) are slower than electronic signals (which travel at the speed of light), thus allowing time for a warning to be issued

What are the components of the early warning system?

• Detection and Network Infrastructure (Seismic network, P-wave detection, rapid date transmission)

• Processing and alert generation (algorithms, shaking forecast)

• Alert delivery (alert transmission, geo-targeting)

• Mitigation Response (personal safety action, automated control)

blind zone

the region surrounding the epicenter of an earthquake where strong shaking has already begun or arrived before an Earthquake Early Warning (EEW) alert can be successfully delivered

What can/cannot be done with some seconds of warning?

A few seconds of warning provided by an Earthquake Early Warning (EEW) system is enough time to take critical actions that can save lives, prevent injuries, and safeguard infrastructure, though it is not enough time for full evacuation or complex responses.

Communicate clearly why early warning not a prediction

it deals with an event that is already in progress, providing a quick alert, rather than specifying when a future event will happen

Explain of how early warning works

EEW systems detect an earthquake that has already nucleated and started (L-20, p. 7). It relies on the arrival of the non-damaging P-wave to estimate the magnitude and location of the ongoing rupture, and then issues a short-term forecast of the more damaging S-waves and surface waves that are still propagating toward populated areas

As learned in class, where else in the world is an early warning system used? Was it useful there? Where in the world was earthquake early warning first deployed?

1. Mexico: In the 1995 Magnitude 7.3 Guerrero earthquake, the system provided 72 seconds of warning in Mexico City. This allowed officials to stop the Metro system 50 seconds before strong shaking arrived and enabled the successful evacuation of school

2. Japan: During the 2011 Magnitude 9.1 Tohoku-Oki earthquake, Tokyo received more than 2 minutes of warning. A survey showed that 90% of the public in the affected region found the system useful. The system has also reduced downtime and economic losses in industrial facilities

Prediction vs forecast

The key difference lies in the time scale and certainty. A forecast provides a long-term probability (e.g., 72% chance over 30 years), while a prediction requires specifying the exact date and time, which science cannot yet do

Prediction vs early warning

• Prediction aims to warn about an event that has not yet occurred. Early warning detects an earthquake that has already started.

Correctly identify whether a statement is a forecast, a prediction, or an early warning

1. If the statement givings a probability of a decade-long period it is a forecast

2. If the statement attempts to specify the exact day and location of a future earthquake, it is a prediction

3. If the statement provides a countdown after shaking has begun or advises immediate protective action, it is an early warning