Permanent project revision
Revision 2026-08-20-source-dates · effective 2026-07-26
Current revision. This is the snapshot used by the live entity page.
Created the first structured Evidence Passport with 1 claim and 10 source dossiers.
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add /evidencePassport — Added claim-level evidence mapping and source dossiers.add /revisionHistory — Established a permanent, hash-addressed baseline revision.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.
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
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.
Awaiting operator and domain-expert review; publication of this revision implies neither.
sha256:e7193a87c4d4d6c02567736110b01c101a09206fb0aa003a2778e4a9ae5b3a82
src-2b2b98cfafb5bf16The 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.
src-191a0d8e04a77d28Source 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.
src-39fe7124655ca2a0BSSA 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.
src-c3fd970571855f3cLaunch 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.
src-29a299841e84f202Dates the change to Wednesday 14 August 2019 and attributes it jointly to Mayor Garcetti and the USGS: magnitude 5.0 down to 4.5.
src-46b7c7e85fc8e498The $300,000 contract with AT&T and the GRYD Foundation for design, creation and deployment of the app.
src-bdc20dd40223dd4eThe city's same-day response to the Ridgecrest non-alert, promising to lower the threshold.
src-b03bb633e85db16eIndependent 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.
src-1606abec73a62cecGarcetti's stated reason, that ShakeAlertLA was a bridge to the statewide system, and confirmation that MyShake is operated by UC Berkeley.
src-81e2b66e5de16c32The 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.