Max Est. MMI
15km WSW of Ferndale, CA
Shaking Animations
Simulated bowling pin shaking at each city’s intensity level. Videos appear as they finish rendering.
BBP Simulation Comparison
How closely a physics-based simulation of this earthquake reproduces what the seismic network actually recorded. The simulation is run on the SCEC Broadband Platform and compared against real seismograms station by station.
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BBP Simulation Comparison
How closely a physics-based simulation of this earthquake reproduces what the seismic network actually recorded. The simulation is run on the SCEC Broadband Platform and compared against real seismograms station by station.
Emulated hardware. The simulation ran on arm64 under emulation. Amplitudes are not SCEC-reference-accurate, and this measurement cannot separate the platform from the model.
Velocity model. Simulated with NoCal500. No installed region is native to this epicentre, so the crustal profile is an approximation.
One realization. A single stochastic rupture, not an ensemble. The bias below is one draw; a second run with a different seed would give a different number.
Defaulted Vs30 at 4 of 31 sites. Those sites were simulated with a Vs30 value repeated across three or more stations — a lookup default rather than a site measurement. Vs30 drives the site term, so a defaulted value produces bias at intermediate and long period that is not the model's fault.
What a pass means. Consistency with recordings at these 31 stations, for this event, under this velocity model, on this hardware, within a factor of 1.99. It is not a general statement about BBP and not a prediction of accuracy at an unrecorded site.
- mean |bias|
- 0.165
- a factor of 1.18×
- pass band
- 0.69
- a factor of 1.99×, declared before the run
- sigma
- 1.244
- station-to-station scatter
- cross-check
- 0.327
- recomputed here from the waveforms
The metric is ln(observed / simulated) RotD50 spectral acceleration, averaged over stations. Positive means the simulation under-predicts — real shaking was larger. Basis: BBP RotD50 residuals (authoritative).
Residual by period
Mean ln(obs/sim) at each spectral period. A structure responds at its own period, so agreement at one period says nothing about another.
| Period | Bias | Simulation | vs. band |
|---|---|---|---|
| 0.1s | -0.512 | over-predicts by 67% | within |
| 0.3s | -0.283 | over-predicts by 33% | within |
| 1s | -0.135 | over-predicts by 14% | within |
| 3s | +0.178 | under-predicts by 19% | within |
Goodness of fit across the spectrum
Mean residual with its ±1σ band, against the pass band. Diamonds are the Broadband Platform’s own RotD50 residuals.
Engineering Ground Motion Parameters
GMPE predictions provide an independent check on the ShakeMap interpolated intensities above.
ShakeMap relies on seismic station recordings; in areas with sparse station coverage — or
for large teleseismic events and earthquakes outside dense West Coast networks — ShakeMap
MMI can be inaccurate. A significant difference between ShakeMap and GMPE estimates is a signal
that the ShakeMap result should be treated as preliminary.
Also includes site Vs30 values and raw ground motion parameters (PGA/PGV).
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Engineering Ground Motion Parameters
GMPE predictions provide an independent check on the ShakeMap interpolated intensities above. ShakeMap relies on seismic station recordings; in areas with sparse station coverage — or for large teleseismic events and earthquakes outside dense West Coast networks — ShakeMap MMI can be inaccurate. A significant difference between ShakeMap and GMPE estimates is a signal that the ShakeMap result should be treated as preliminary. Also includes site Vs30 values and raw ground motion parameters (PGA/PGV).
Est. Vs30 Values
Estimated shear-wave velocity in the upper 30 m used in GMPE calculations. Ref. column shows the 760 m/s rock-site reference for comparison.
| Location | Ref. (760 m/s) | Est. Vs30 (m/s) |
|---|---|---|
|
Hydesville
CA |
760 | 468 |
|
Rio Dell
CA |
760 | 468 |
|
Fortuna
CA |
760 | 418 |
|
Ferndale
CA |
760 | 273 |
|
Humboldt Hill
CA |
760 | 370 |
|
Bayview
CA |
760 | 350 |
|
Cutten
CA |
760 | 359 |
|
Myrtletown
CA |
760 | 354 |
|
Pine Hills
CA |
760 | 369 |
|
Bayside
CA |
760 | 357 |
|
Eureka
CA |
760 | 280 |
|
Arcata
CA |
760 | 351 |
|
Blue Lake
CA |
760 | 352 |
|
Redway
CA |
760 | 352 |
|
McKinleyville
CA |
760 | 373 |
|
Westhaven-Moonstone
CA |
760 | 411 |
|
Hayfork
CA |
760 | 351 |
|
Willow Creek
CA |
760 | 733 |
MMI vs Distance — Default Vs30 (760 m/s)
All methods using the 760 m/s rock-site reference. ShakeMap values are independent of Vs30.
MMI vs Distance — Est. Vs30
GMPEs use the Est. Vs30 values shown in the table above. ShakeMap values are independent of Vs30.
GMPE Residual — Observed − Predicted MMI
Signed residual at each seismic station. Positive values mean the GMPE underestimated shaking; negative values mean it overestimated. The dashed line at zero indicates perfect agreement.
GMPE Predicted vs. Observed MMI at Seismic Stations
Each point is one seismic station. Points on the dashed 1:1 line indicate perfect agreement; above the line = GMPE underestimated shaking; below = overestimated.
GMPE Performance — Station Observations
Statistics computed by comparing each GMPE's predicted MMI against ShakeMap observed MMI at seismic stations. Bias = mean(observed − predicted). Lower RMSE indicates better overall agreement with instrumental measurements.
| GMPE | Bias | Sigma | RMSE |
|---|---|---|---|
| ASK14 | +1.34 | 0.82 | 1.57 |
| BSSA14 | +1.50 | 0.75 | 1.68 |
| CY14 | +1.28 | 0.80 | 1.50 |
| CB14 | +1.26 | 0.82 | 1.50 |
Peak Ground Motion — Seismic Station Observations
Recorded PGA and PGV at seismic stations, sorted by highest PGA. Top 25 stations shown. MMI (PGA) and MMI (PGV) are independent conversions via Worden et al. (2012) GMICE.
| Station | PGA (g) | MMI (PGA) | PGV (cm/s) | MMI (PGV) |
|---|---|---|---|---|
| Rio Dell (CE.89462) | 1.4387 | Very Strong(VII) | 63.425 | Extreme(X) |
| Fortuna (CE.89255) | 0.8010 | Strong(VI) | 34.755 | Violent(IX) |
| College of the Redwoods (NP.1582) | 0.4536 | Strong(VI) | 34.115 | Violent(IX) |
| Fortuna (CE.89486) | 0.3938 | Strong(VI) | 28.695 | Severe(VIII) |
| Loleta Fire Station (NP.1586) | 0.3000 | Moderate(V) | 25.784 | Severe(VIII) |
| Eureka (CE.89641) | 0.2959 | Moderate(V) | 21.361 | Severe(VIII) |
| South Bay School (NP.1581) | 0.2748 | Moderate(V) | 32.524 | Violent(IX) |
| Fire Station (NP.1023) | 0.2561 | Moderate(V) | 22.278 | Severe(VIII) |
| Bunker Hill, NOAA Radar (NP.1584B) | 0.2212 | Moderate(V) | 10.324 | Very Strong(VII) |
| Paradise Ridge (BK.PRDS) | 0.1806 | Moderate(V) | 9.706 | Very Strong(VII) |
| Kneeland/Ashfield Ridge (BK.KNEE) | 0.1636 | Moderate(V) | 39.187 | Violent(IX) |
| Pringle Ridge (NC.KPR) | 0.1402 | Moderate(V) | 15.552 | Severe(VIII) |
| Burgh Ranch (NC.KBU) | 0.1382 | Moderate(V) | 18.543 | Severe(VIII) |
| Bald Jesse, Humboldt County, CA (BK.BJES) | 0.1254 | Moderate(V) | 21.984 | Severe(VIII) |
| Horse Mountain (NC.KHMB) | 0.1253 | Moderate(V) | 15.092 | Severe(VIII) |
| Cape Town (NC.KCT) | 0.1239 | Moderate(V) | 30.028 | Violent(IX) |
| Mount Pierce (NC.KMPB) | 0.1237 | Moderate(V) | 11.679 | Very Strong(VII) |
| Punta Gorda, Petrolia, CA (BK.PETL) | 0.1236 | Moderate(V) | 8.521 | Very Strong(VII) |
| Cooskie Peak (NC.KCO) | 0.1201 | Moderate(V) | 15.272 | Severe(VIII) |
| Tule Creek, Hayfork, CA (BK.HAYF) | 0.1037 | Moderate(V) | 8.198 | Very Strong(VII) |
| Garberville CALFire station (NP.1591) | 0.0950 | Moderate(V) | 9.032 | Very Strong(VII) |
| Cold Springs (NC.KCSB) | 0.0868 | Moderate(V) | 12.725 | Very Strong(VII) |
| Rainbow Ridge, Humboldt, CA (BK.RBOW) | 0.0795 | Moderate(V) | 10.511 | Very Strong(VII) |
| Briceland Vineyard, Redway, CA (BK.BRIC) | 0.0752 | Moderate(V) | 7.824 | Very Strong(VII) |
| Mail Ridge (NC.KMR) | 0.0721 | Moderate(V) | 9.469 | Very Strong(VII) |
Ground Shaking Intensities — Interpolated ShakeMap MMI
18 sites| Location | MMI Description |
|---|---|
|
Hydesville
CA |
Very Strong(VII) |
|
Rio Dell
CA |
Very Strong(VII) |
|
Fortuna
CA |
Strong(VI) |
|
Ferndale
CA |
Strong(VI) |
|
Humboldt Hill
CA |
Strong(VI) |
|
Bayview
CA |
Strong(VI) |
|
Cutten
CA |
Strong(VI) |
|
Myrtletown
CA |
Strong(VI) |
|
Pine Hills
CA |
Strong(VI) |
|
Bayside
CA |
Moderate(V) |
|
Eureka
CA |
Moderate(V) |
|
Arcata
CA |
Moderate(V) |
|
Blue Lake
CA |
Moderate(V) |
|
Redway
CA |
Moderate(V) |
|
McKinleyville
CA |
Moderate(V) |
|
Westhaven-Moonstone
CA |
Light(IV) |
|
Hayfork
CA |
Light(IV) |
|
Willow Creek
CA |
Light(IV) |
Seismic Station Observed MMI
MMI values are derived directly from observed ground motion measurements at seismic stations and are not spatially interpolated.