1001 Smart Cities
🇺🇸 Los Angeles

ShakeAlertLA — the City's Earthquake Warning App

🤖 AI-generated summary · ◆ 1 sourced claim · 🔎 Last verified

This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.

1 sourced claim on this page, none individually verified yet — turn on “Sources in the text” to see each one.

How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page

The first US smartphone app relaying federal earthquake warnings sent no alert to Los Angeles during the July 2019 Ridgecrest quakes. The city's threshold was too high; the algorithm underestimated the magnitude by 0.8 units.

Outcome📉 Scaled back
Evidence🔬 Peer-reviewed
what does this mean?The strongest source behind this entry is an independent peer-reviewed or academic study. It grades who did the looking — not how well the project went. All four grades →
Run byCity of Los Angeles (Information Technology Agency and Emergency Management Department); alerts from the USGS ShakeAlert system
Scale🗺️ Regional
Cost≈$300k app contract (AT&T and the GRYD Foundation)
FundingCity of Los Angeles contract, with the Annenberg Foundation and the Mayor's Fund for Los Angeles as named partners

Part of 1001 Smart Cities — 1,167 documented projects · 🏙️ 12 more in Los Angeles · 🛡️ Safety & security guide · 🏛️ Governance projects

Los Angeles released the first publicly available US smartphone app relaying earthquake warnings from the federal USGS ShakeAlert system, on the app stores from 31 December 2018. The sensors and the alert algorithm were federal; the city paid for the app and chose its alert threshold. It retired the app on 31 December 2020 for California's statewide MyShake.

Completed 📅 2018–2020

📊 Impact

During the July 2019 Ridgecrest sequence — a M6.4 foreshock and a M7.1 mainshock, California's largest quake in 20 years — the app sent no public alert to Los Angeles County. A peer-reviewed USGS-authored analysis found the predicted shaking fell below the app's MMI 4.0 threshold, and that for the M7.1 an alert was warranted but ShakeAlert underestimated the magnitude by 0.8 units. The city cut the trigger from magnitude 5.0 to 4.5 on 14 August 2019. It reported 920,000 downloads over two years; no documented case of the app warning Angelenos before shaking was found.

🎓 Lesson

Los Angeles could set the alert threshold but not the accuracy behind it. At Ridgecrest both failed at once: the city's threshold was too high, and the federal algorithm underestimated the quake by 0.8 magnitude units.

🏛️ GovernanceSafety & securitySensors & IoTDigital government

Sources

↗ City of Los Angeles Information Technology Agency (authority)Published 18 January 2019The city's own account of the release, built on the USGS ShakeAlert system, and of the later lowering of the warning threshold from magnitude 5.0 to 4.5. Dates the release to 1 January 2019; the app reached the stores on 31 December 2018.
↗ Cal OES / Mayor Garcetti — retirement announcement (23 Dec 2020)Source of the 31 December 2020 retirement date, the self-reported 920,000 downloads and 100,000 alerts issued, the AT&T / Annenberg Foundation / Mayor's Fund partnership, and the statement that the statewide system pairs MyShake with Wireless Emergency Alerts.
↗ Chung et al., Bulletin of the Seismological Society of America (2020) — peer-reviewedPublished 20 July 2020 archived copyBSSA 110(4):1904-1923, doi 10.1785/0120200032. Carries both load-bearing findings: no public alert was sent because predicted shaking was below the app's MMI 4.0 threshold, and for the M7.1 an alert was warranted but the point-source and finite-fault algorithms underestimated the magnitude by 0.8 units. Also confirms the app was the only publicly available alerting method at the time. Publisher pages block automated fetching (403); text verified via indexed abstract.
↗ GovTech — ShakeAlertLA adjusts alert thresholds after users complainPublished 8 July 2019Launch threshold of magnitude 5.0 plus MMI IV, and the city's own rationale for setting it high: officials feared people would become apathetic and stop responding if it was set too low. Reports the MMI threshold as unchanged, which is why no revised intensity value is claimed here.
↗ NBC Los Angeles — threshold lowered (14 Aug 2019)Updated 15 August 2019Dates the change to Wednesday 14 August 2019 and attributes it jointly to Mayor Garcetti and the USGS: magnitude 5.0 down to 4.5.
Show 5 more sourcesShow fewer
↗ CBS Los Angeles — city council approves the app contract (19 Jun 2018)The $300,000 contract with AT&T and the GRYD Foundation for design, creation and deployment of the app.
↗ CBS Los Angeles — 'We hear you' (4 Jul 2019)The city's same-day response to the Ridgecrest non-alert, promising to lower the threshold.
↗ Nextgov — L.A.'s public earthquake-warning app is the first in the U.S. (Jan 2019)Published 8 January 2019Independent support for the first-in-the-nation claim and for the partner list; also records that dozens of early users reported the iPhone app crashing at launch.
↗ LAist — the city points everyone to the statewide app (Dec 2020)Published 23 December 2020Garcetti's stated reason, that ShakeAlertLA was a bridge to the statewide system, and confirmation that MyShake is operated by UC Berkeley.
↗ Temblor — earthquake early warning now and beyondPublished 20 December 2022The only quantified Los Angeles performance figures found, and they belong to the successor app: at the M4.5 El Monte quake of 19 September 2020, MyShake sent 20,169 alerts, reached 80% of phones 3.5 seconds after receiving the ShakeAlert signal, and about half of alerted users were notified before the S-wave arrived. Also identifies WEA as FEMA's channel.

📅 How old is the evidence?

Two clocks, kept apart: when this entry’s sources were published, and what has happened to its record in the atlas. Documented span: 2018–2020. 10 of 10 sources carry a publication date, from 19 June 2018 to 20 December 2022.

When the sources were published

  1. CBS News · pressCBS Los Angeles — city council approves the app contract (19 Jun 2018)
  2. Nextgov/FCW (GovExec) · pressNextgov — L.A.'s public earthquake-warning app is the first in the U.S. (Jan 2019)
  3. City of Los Angeles Information Technology Agency · city governmentCity of Los Angeles Information Technology Agency (authority)
  4. CBS News · pressCBS Los Angeles — 'We hear you' (4 Jul 2019)
  5. Government Technology (e.Republic) · pressGovTech — ShakeAlertLA adjusts alert thresholds after users complain
  6. NBC Los Angeles · pressNBC Los Angeles — threshold lowered (14 Aug 2019) · updated 15 August 2019
  7. U.S. Geological Survey (USGS) · national governmentChung et al., Bulletin of the Seismological Society of America (2020) — peer-reviewed
  8. California Governor's Office of Emergency Services · regional governmentCal OES / Mayor Garcetti — retirement announcement (23 Dec 2020)
Show 2 more dated sourcesShow fewer
  1. LAist · pressLAist — the city points everyone to the statewide app (Dec 2020)
  2. Temblor · pressTemblor — earthquake early warning now and beyond

Every source, with links ↑

What happened to this record

  1. Sources last read
  2. Entered the record

Every revision, permanent →

Show your work What this page rests on and what it can’t tell you · all 1 claims with their sources · the forensic record

Evidence Passport · public beta 1 addressable claim, 10 source dossiers, one permanent baseline. The passport is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.

Inspect the claims, one by one — verbatim text, sources and caveats for all 1

The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.

Claim 1 clm-c7485f5c2f00dfe4 quantitative
A peer-reviewed USGS-authored analysis found the predicted shaking fell below the app's MMI 4.0 threshold, and that for the M7.1 an alert was warranted but ShakeAlert underestimated the magnitude by 0.8 units
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The analysis covers the July 2019 Ridgecrest sequence, during which the app sent no public alert to Los Angeles County.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Chung et al., Bulletin of the Seismological Society of America (2020) — peer-reviewed
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders

This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.

unreviewed Revision 2026-08-20-source-dates effective 2026-07-26 · created 2026-08-20

Awaiting operator and domain-expert review; publication of this revision implies neither.

sha256:e7193a87c4d4d6c02567736110b01c101a09206fb0aa003a2778e4a9ae5b3a82
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
1
of 1 claims mapped
10
source dossiers
10
publication dates recorded
1
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
City of Los Angeles (Information Technology Agency and Emergency Management Department); alerts from the USGS ShakeAlert system
Actor types
city-government, national-government
Funding model
mixed
Funding description
City of Los Angeles contract, with the Annenberg Foundation and the Mayor's Fund for Los Angeles as named partners
Cost
≈$300k app contract (AT&T and the GRYD Foundation)
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

10 source dossiers

City of Los Angeles Information Technology Agency (authority) ita.lacity.gov · background

Open original source ↗

Stable source ID
src-2b2b98cfafb5bf16
Publisher
Name not classified · ita.lacity.gov
Type / language
web-page · language not classified
Published
2019-01-18
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The city's own account of the release, built on the USGS ShakeAlert system, and of the later lowering of the warning threshold from magnitude 5.0 to 4.5. Dates the release to 1 January 2019; the app reached the stores on 31 December 2018.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Cal OES / Mayor Garcetti — retirement announcement (23 Dec 2020) news.caloes.ca.gov · background

Open original source ↗

Stable source ID
src-191a0d8e04a77d28
Publisher
Name not classified · news.caloes.ca.gov
Type / language
web-page · language not classified
Published
2020-12-23
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Source of the 31 December 2020 retirement date, the self-reported 920,000 downloads and 100,000 alerts issued, the AT&T / Annenberg Foundation / Mayor's Fund partnership, and the statement that the statewide system pairs MyShake with Wireless Emergency Alerts.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Chung et al., Bulletin of the Seismological Society of America (2020) — peer-reviewed usgs.gov · 1 linked claim

Open original source ↗

Stable source ID
src-39fe7124655ca2a0
Publisher
Name not classified · usgs.gov
Type / language
web-page · language not classified
Published
2020-07-20
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
Open archived copy ↗ · 2026-02-12
Content hash
No captured content hash
Locator
Open the recorded source note

BSSA 110(4):1904-1923, doi 10.1785/0120200032. Carries both load-bearing findings: no public alert was sent because predicted shaking was below the app's MMI 4.0 threshold, and for the M7.1 an alert was warranted but the point-source and finite-fault algorithms underestimated the magnitude by 0.8 units. Also confirms the app was the only publicly available alerting method at the time. Publisher pages block automated fetching (403); text verified via indexed abstract.

Descriptive only — not page/paragraph exact
Claims linked
GovTech — ShakeAlertLA adjusts alert thresholds after users complain govtech.com · background

Open original source ↗

Stable source ID
src-c3fd970571855f3c
Publisher
Name not classified · govtech.com
Type / language
web-page · language not classified
Published
2019-07-08
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Launch threshold of magnitude 5.0 plus MMI IV, and the city's own rationale for setting it high: officials feared people would become apathetic and stop responding if it was set too low. Reports the MMI threshold as unchanged, which is why no revised intensity value is claimed here.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
NBC Los Angeles — threshold lowered (14 Aug 2019) nbclosangeles.com · background

Open original source ↗

Stable source ID
src-29a299841e84f202
Publisher
Name not classified · nbclosangeles.com
Type / language
web-page · language not classified
Published
2019-08-14
Updated
2019-08-15
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Dates the change to Wednesday 14 August 2019 and attributes it jointly to Mayor Garcetti and the USGS: magnitude 5.0 down to 4.5.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
CBS Los Angeles — city council approves the app contract (19 Jun 2018) cbsnews.com · background

Open original source ↗

Stable source ID
src-46b7c7e85fc8e498
Publisher
Name not classified · cbsnews.com
Type / language
web-page · language not classified
Published
2018-06-19
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The $300,000 contract with AT&T and the GRYD Foundation for design, creation and deployment of the app.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
CBS Los Angeles — 'We hear you' (4 Jul 2019) cbsnews.com · background

Open original source ↗

Stable source ID
src-bdc20dd40223dd4e
Publisher
Name not classified · cbsnews.com
Type / language
web-page · language not classified
Published
2019-07-04
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The city's same-day response to the Ridgecrest non-alert, promising to lower the threshold.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Nextgov — L.A.'s public earthquake-warning app is the first in the U.S. (Jan 2019) nextgov.com · background

Open original source ↗

Stable source ID
src-b03bb633e85db16e
Publisher
Name not classified · nextgov.com
Type / language
web-page · language not classified
Published
2019-01-08
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Independent support for the first-in-the-nation claim and for the partner list; also records that dozens of early users reported the iPhone app crashing at launch.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
LAist — the city points everyone to the statewide app (Dec 2020) laist.com · background

Open original source ↗

Stable source ID
src-1606abec73a62cec
Publisher
Name not classified · laist.com
Type / language
web-page · language not classified
Published
2020-12-23
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Garcetti's stated reason, that ShakeAlertLA was a bridge to the statewide system, and confirmation that MyShake is operated by UC Berkeley.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Temblor — earthquake early warning now and beyond temblor.net · background

Open original source ↗

Stable source ID
src-81e2b66e5de16c32
Publisher
Name not classified · temblor.net
Type / language
web-page · language not classified
Published
2022-12-20
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-20
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The only quantified Los Angeles performance figures found, and they belong to the successor app: at the M4.5 El Monte quake of 19 September 2020, MyShake sent 20,169 alerts, reached 80% of phones 3.5 seconds after receiving the ShakeAlert signal, and about half of alerted users were notified before the S-wave arrived. Also identifies WEA as FEMA's channel.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Known limits of this passport
  • Publisher names and source languages have not yet been classified; domains are recorded without guessing.
  • Existing source notes are descriptive locators, not page- or paragraph-exact citations.
  • A missing archive, publication date or content hash is shown as null rather than inferred.
  • The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.

Continue exploring

Compare this project

🇹🇷 Earthquake Early Warning & Seismic Monitoring Network · Istanbul Same hazard, opposite ends of the chain: Istanbul's seismic net halts trains and gas by itself; LA's app pushed a notification, or didn't. 🇯🇵 Tsunami-Alert Automatic Tide Gate Closure · Osaka A national alert closes Osaka's gates with nobody deciding; the same kind of national alert reached LA, and a city threshold stopped it. 🇵🇭 EFCOS: Metro Manila's Flood Telemetry and Floodway Gates · Manila Both put a number between sensor and response: Manila's crews open gates on a gauge; LA's threshold was set high enough that nothing fired.

Explore the wider context

📟 A Reading Is Not a Decision📖 Automated speed enforcement (speed cameras)📖 Flood early-warning system📖 Integrated command and control centre (ICCC)
📎 Cite this project

1001 Smart Cities (2026). “ShakeAlertLA — the City's Earthquake Warning App” — Los Angeles, United States. The Smart City Atlas. https://1001smartcities.org/projects/la-shakealert-app/ (last verified 2026-07-26). Data: CC BY 4.0.

The underlying data is free to reuse with attribution — see the open data page.

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