← Daily DoseFaster Than the Shaking — Daily Dose No. 061
Daily Dose / Sep 14, 2026 / Earthquake Warning
Faster Than the Shaking
An earthquake cannot be predicted. But once it starts, it can be outrun — not by people, by electrons. The rupture crawls outward through rock at a few kilometres a second. The warning about it travels at the speed of light. Everything earthquake early warning does lives inside that gap.
75,000×
An alert moving through fibre and radio travels roughly 300,000 km/s. The destructive S-wave travels about 4 km/s. The message wins the race by four and a half orders of magnitude — which is why a phone in Istanbul can buzz 56 seconds before the ground arrives.
01 · The Physics
The race you can't see
A fault slips. Fast, weak P-waves radiate first; slower, damaging S-waves and surface waves follow. A seismometer catches the P-wave, a processing centre estimates location and size, and the answer is transmitted electronically — down a path that is tens of thousands of times faster than the rock it is describing.
USGS ShakeAlert: P-waves ≈ 3.7 mi/s, S- and surface waves ≈ 2.5 mi/s. The alert-signal bar runs off a log axis on purpose — that is the point.
02 · The Blind Zone
Zero seconds, if you're close
The warning is not free. Detecting the P-wave, estimating magnitude and pushing the message out consumes several seconds — and in those seconds the shaking has already covered ground. Everyone inside that radius gets the alert during or after the shaking. The nearer you are to the fault, the less the system can do for you.
Illustrative model S-wave at 4.0 km/s, alert delivered 8 s after rupture begins. Not measured data — real lead times vary with depth, network density and delivery path.
What the record shows
Across 2019–2023, ShakeAlert delivered 0 to 12 seconds of warning at places that went on to feel severe MMI 8 shaking, 0 to 17 seconds at MMI 7 sites, and 0 to 23 seconds at MMI 6 sites. The hardest-hit places get the least notice — a structural feature of the physics, not a bug in the software.
In the same window the system caught 41 of 53 M4.5+ earthquakes inside its alerting boundary and ran a 7.4% false-alert rate, under its own 10% standard, with no false alerts at M5+.
Lux et al., Bulletin of the Seismological Society of America, 2024
03 · The Scale
What the shaking does
Magnitude describes the earthquake. Intensity describes your street. The Modified Mercalli scale, written in 1931, is still the ladder that alerting thresholds are hung on — ShakeAlert starts warning the public around intensity III, and escalates its language at V.
III
< 0.03 g
Felt indoors. Like a truck passing. Many don't call it an earthquake.
ALERT THRESHOLD
IV
< 0.03 g
Dishes and windows rattle. Parked cars rock noticeably.
V
0.03–0.08 g
Felt by nearly everyone. Sleepers wake. Unstable objects fall.
URGENT LANGUAGE
VI
0.08–0.15 g
Felt by all. Heavy furniture moves; plaster falls. Damage slight.
0–23 s WARNING
VII
0.15–0.25 g
Considerable damage to poorly built structures. Chimneys break.
0–17 s WARNING
VIII
0.25–0.45 g
Partial collapses. Walls thrown out of frame structures.
MMI descriptions: Wood & Neumann, 1931, as used by USGS. Peak-ground-acceleration bands are the standard approximate ShakeMap correspondence. Observed warning windows: Lux et al., BSSA 2024.
04 · The Record
Seconds, actually delivered
Design targets are one thing. These are lead times that real systems have put in front of real people — and the spread between them is almost entirely a function of how far the shaking had to travel.
Sources: CIRES/SASMEX via Eos, 2018 · Nature Communications, 2026 · Lux et al., BSSA 2024 · JR East / JSCE. Bars shade light→dark with decreasing warning.
05 · The Build-Out
From one city to ninety-eight countries
For thirty years, early warning was a public work: dedicated seismometers, dedicated sirens, one country at a time. Then the accelerometer already in two billion pockets turned into a seismic network, and coverage went up tenfold in about four years.
1991
Mexico's SASMEX goes live — the world's first public earthquake warning system, built after the 1985 quake.
2007
Japan's JMA begins nationwide public Earthquake Early Warning, after a year of alerts to advanced users.
2019
ShakeAlert opens to the public in California.
2021
ShakeAlert reaches Oregon and Washington — 50M+ people. Android Earthquake Alerts begins global rollout.
2023
Android alerting is live in 98 countries; 2.5 billion people now have some form of earthquake early warning.
2025
ShakeAlert's seismic sensor build-out reaches its planned 1,675-station target.
THE RING, AND WHO WATCHES IT
Schematic map — hand-simplified outlines, not survey-accurate. Dates mark public alerting milestones.
PEOPLE WITH EARLY-WARNING ACCESS
250M→2.5B
Android Earthquake Alerts detected more than 18,000 earthquakes from M1.9 to M7.8, issued alerts for over 2,000 of them, and delivered 790 million individual alerts. Its median magnitude error fell from 0.50 to 0.25 in three years — the network learned.
Allen, Stogaitis et al., Science, 2025
SHAKEALERT SEISMIC STATIONS
Plus ~1,100 geodetic stations. USGS, Dec 2024.
06 · The Stakes
What the seconds are worth
Earthquakes are not the most frequent disaster. Over two decades they were by a wide margin the deadliest — and the cost is concentrated into the moments when unreinforced walls meet ground acceleration.
747,234
Deaths, 1998–2017
From 563 earthquakes and related tsunamis — 56% of all disaster deaths worldwide in those twenty years.
$661.5B
Recorded losses, 1998–2017
Earthquakes and tsunamis, in reported economic damage. The true figure is higher; much goes unrecorded.
$34.2B
Türkiye, February 2023
Direct physical damage from two quakes in one morning — about 4% of Türkiye's 2021 GDP, plus $5.1B in Syria. Roughly 56,000 people died.
27
Trains that stopped
Shinkansen running on the Tōhoku line in 2011. Power cut automatically, 275 km/h down to 70. No derailments.
The 1985 debt
Mexico's system exists because of one morning. The M8.1 Michoacán earthquake of 19 September 1985 killed more than 9,000 people in Mexico City and left over 100,000 homeless — from an epicentre some 350 km away. That distance is exactly what makes warning possible there: today, 12,000 pole-mounted speakers can sound roughly a minute before a coastal quake arrives. When the M7.1 struck near Puebla on 19 September 2017 — the same date, 32 years on — the epicentre was only 120 km out, and the city got about 20 seconds.
What to do with ten seconds
It is not enough time to leave. It is enough time to survive.
Turn the alerts on.On Android: Settings → Safety & emergency → Earthquake alerts. It is on by default in most of the 98 covered countries, but check. In the US, keep government Wireless Emergency Alerts enabled, and consider the MyShake app on either platform.
Drop, cover, hold on.The instinct to run outside is the wrong one — doorways and stairwells are where people get hurt. Ten seconds buys you the distance to a sturdy table, away from windows. That is the intended use of the warning.
Most of the value isn't human.Seconds are enough for a train to brake, an elevator to stop at the nearest floor and open, a gas valve to close, a surgeon to lift the scalpel, a production line to safe itself. Automated response is where early warning does its heaviest lifting.
If you live near the fault, assume zero.Inside the blind zone the alert arrives with — or after — the shaking. Nothing replaces strapping the water heater, anchoring the bookcase and knowing whether your building was built to code. Warning is the last layer, not the first.
Sources & notes
U.S. Geological Survey, "Earthquake Early Warning — Overview" and ShakeAlert fact sheets (2021–2025). P-waves ≈ 3.7 mi/s (≈6.0 km/s); S- and surface waves ≈ 2.5 mi/s (≈4.0 km/s). Alerts available to more than 50 million people in California, Oregon and Washington; public alerting from October 2019 (CA) and 4 May 2021 (OR, WA); alerting threshold M4.5 / MMI III, with escalated language at MMI V.
Lux, A. I., et al., "Status and Performance of the ShakeAlert® Earthquake Early Warning System: 2019–2023," Bulletin of the Seismological Society of America, 2024. Warning times 0–12 s at MMI 8 sites, 0–17 s at MMI 7, 0–23 s at MMI 6; 41 of 53 M4.5+ earthquakes detected within the alerting boundary (22.6% missed); 7.4% false-alert rate; 1,509 stations ingested; 1,675-station target in the Technical Implementation Plan.
USGS ShakeAlert network status, December 2024. 1,553 seismic stations and approximately 1,100 geodetic stations across CA, OR and WA; seismic build-out expected complete by end of 2025. 2012 baseline of roughly 700 stations per the same programme history.
Allen, R. M., Stogaitis, M., et al., "Global earthquake detection and warning using Android phones," Science, July 2025 (doi:10.1126/science.ads4779); Google Research technical summary. Alerting in 98 countries for M≥4.5; global early-warning access expanded from ~250 million to ~2.5 billion people; 790 million alerts delivered; more than 18,000 earthquakes detected, M1.9–M7.8; alerts issued for over 2,000; median absolute magnitude error improved from 0.50 to 0.25 over three years; 85% of more than 1.5 million survey respondents rated alerts very helpful.
"Performance and user response of Android's smartphone-based alerts in the 2025 Marmara Ereğlisi earthquake," Nature Communications, 2026. M6.2 event detected 5.31 s after initiation; more than 16 million users alerted; median warning time 56 s for weak shaking, reaching 150 s at the far edge.
Eos (American Geophysical Union), "Lessons from Mexico's Earthquake Early Warning System," 2018, and CIRES/SASMEX programme material. Public alerting from 1991, the first such system in the world; ~60 s design warning to Mexico City for coastal subduction earthquakes; 12,000 pole-mounted speakers; the 19 September 2017 M7.1 Puebla earthquake, 120 km from the city, gave roughly 20 s before S-wave arrival.
Eos (2018); Britannica; USGS on the 19 September 1985 M8.1 Michoacán earthquake. More than 9,000 killed and more than 100,000 left homeless in Mexico City. Higher death-toll estimates exist and remain disputed; the conservative figure is used here.
Japan Society of Civil Engineers, "Earthquake Early Warning System for Railways and its Performance"; JR East operational reports on the 11 March 2011 M9.0 Tōhoku earthquake. 27 Shinkansen were running on the Tōhoku line; power was cut and brakes applied automatically, from 275 km/h to 70 km/h; no derailments. Lead time before the braking threshold: 12–22 s.
CRED / UNDRR, "Economic Losses, Poverty & Disasters 1998–2017" (EM-DAT, 2018). 563 earthquakes and related tsunamis caused 747,234 deaths — 56% of all disaster deaths in the period — and US$661.5 billion in recorded economic losses.
World Bank Global Rapid Damage and Needs Assessment, February 2023. US$34.2 billion in direct physical damage in Türkiye (≈4% of 2021 GDP) and US$5.1 billion in Syria from the 6 February 2023 earthquakes; recovery costs are expected to be substantially larger. Combined official death toll approximately 56,000.
Wood, H. O. & Neumann, F., "Modified Mercalli Intensity Scale of 1931." Intensity descriptions as summarised by USGS. Peak-ground-acceleration bands are the standard approximate ShakeMap correspondence (MMI IV and below ≤0.03 g; V 0.03–0.08 g; VI 0.08–0.15 g; VII 0.15–0.25 g; VIII 0.25–0.45 g; IX 0.45–0.60 g) and are conversions, not fixed definitions.
Illustrative modelThe warning-time-versus-distance curve in section 02 is a simple physical model, not measured data. It assumes an S-wave speed of 4.0 km/s and an alert delivered 8 s after rupture initiation, giving a blind-zone radius of about 32 km. It is drawn to show why the blind zone exists; real lead times depend on focal depth, station density, processing version and delivery path. The 75,000× headline is a computed ratio of an electronic alert at ~300,000 km/s to an S-wave at ~4.0 km/s, using the USGS speeds cited above.