Initial MMI 3
M 4.0 - 54 km WNW of Petrolia, CA
- 2024-12-09 07:15:42 (UTC)
- 40.349°N 124.918°W
- 10.0 km depth
ShakeAlert ®
Catalog | Time |
---|---|
EW | 07:19:47 |
- The data below are the most preferred data available
- The data below have been reviewed by a scientist
Post ShakeAlert ® Message Summary
This report provides an overview of the performance of the ShakeAlert system during this event.
Reviewed: ShakeAlert Message issued at 2024-12-09 07:15:57.5 UTC. Results in this summary are preliminary. Alert may not have been sent to the shaken area.
Earthquake
- Title
- M 3.9 - 43.8 mi W of Fortuna
- Time
- 2024-12-09 07:15:41.030 (UTC)
- ShakeAlert Event ID
- ew1733728550
Summary Report
- ShakeAlert Messages Issued (after origin time):
- Initial: 16.5 s
- Peak: 16.5 s
- Final: 26.7 s
- ShakeAlert System Magnitude Estimates:
- Initial: M 4.2
- Peak: M 4.2
- Final: M 4.0
- ANSS report: 165 s after origin, M3.9
- ShakeAlert System Location Accuracy:
- Initial: 30 km (18 mi) WSW
- Peak: 30 km (18 mi) WSW
- Final: 28 km (17 mi) WSW
- Wireless Emergency Alert:
- Magnitude below threshold for WEA system.
- WEA alerts are distributed to the MMI 4+ area if ShakeAlert Peak M >= 5.0
- Number of Stations Reporting:
- 0 within 10km of epicenter
- 4 within 100km of epicenter
- 29 used in final ShakeAlert update
City | Distance | Time* | Shaking (MMI**) |
---|---|---|---|
Fortuna | 70 km (44 mi) | — | Not felt (I) |
Eureka | 81 km (50 mi) | — | Not felt (I) |
Fort Bragg | 141 km (87 mi) | — | Not felt (I) |
Sacramento | 356 km (221 mi) | — | Not felt (I) |
Radius shaken before Message release: 59 km (36 mi)
Figure 1. ShakeAlert initial earthquake location (black dot). Star is ANSS earthquake epicenter. Polygon approximates the outer range for felt ground motion. If shown, red circle is front of peak shaking when the Message was released***. Shaking takes 10 s to expand from circle to circle. Figure 2. Polygons show shaking intensity contours for the peak magnitude estimate. Shaking of MMI 3 or less is often not felt. Star shows the ANSS earthquake epicenter.
Footnotes
- * Time — Time from message release to predicted S-wave arrival at the location. "—" for weak or imperceptable shaking.
- ** MMI — Modified Mercalli Intensity: a numeric shaking severity scale
- *** For earthquakes deeper than ~15 km, the ShakeAlert Message may be available before peak shaking reaches the surface.