Back to M6.0 — The 2014 South Napa, California Earthquake

Observed vs Simulated — Goodness of Fit

A physics-based simulation of this earthquake, compared against the seismograms the network actually recorded. M6.02 The 2014 South Napa, California Earthquake · 2014-08-24 10:20:44 UTC

Download the full report (PDF) Includes per-station waveform and displacement pages. Generated 2026-08-04T20:35:12Z · BBP job job_7b20ecd07ce6408394a3

Before reading the result

What this measurement does and does not establish.

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.

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.

What a pass means. Consistency with recordings at these 40 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.

Result

Mean within pass band 40 stations · 63 spectral periods · BBP simulated

mean |bias|: 0.544; a factor of 1.72×
pass band: 0.69; a factor of 1.99×, declared before the run
sigma: 0.888; station-to-station scatter
cross-check: 0.835; 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	Factor	vs. band
0.1s	-1.245	over-predicts by 247%	3.47×	outside band
0.3s	-0.876	over-predicts by 140%	2.4×	outside band
1s	-0.901	over-predicts by 146%	2.46×	outside band
3s	-0.240	over-predicts by 27%	1.27×	within

Read the mean with this in mind. The mean is within the pass band, but the residual at 0.1s, 0.3s, 1s are outside it — the simulation over-predicts by 247% at 0.1s. A single mean over periods cannot represent that.

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; the line is this report’s independent recomputation from the waveforms.

Where the stations are

Each station coloured by its PGA residual. Red means the simulation under-predicted the recording; blue means it over-predicted.

Map of compared stations coloured by residual

Station summary — three independent sources

40 stations with both a recording and a simulated seismogram. Scroll sideways for the full set of columns.

Station	Dist (km)	Vs30 BBP	Vs30 ShakeMap	Chan	PGA (g) ShakeMap	PGA (g) obspy	PGA (g) BBP	PGV (cm/s) ShakeMap	PGV (cm/s) obspy	PGV (cm/s) BBP	PGD (cm) obspy	PGD (cm) BBP	PGD obs/sim	ln(obs/ sim)	Flags
NC.NHC	4.0	205	205	HNE	0.4029	0.3920	0.4443	59.8	57.4	31.0	22.03	8.08	2.73x	-0.125	—
CE.68150	6.9	272	272	HNE	0.3580	0.3700	0.3915	54.8	55.6	27.7	16.36	6.56	2.50x	-0.056	—
NC.N016	9.6	291	291	HNE	0.6468	0.6101	0.3858	34.4	46.9	23.8	14.77	9.24	1.60x	+0.458	—
YK.KRE	10.1	674	674	ENE	0.3408	0.3491	0.3521	25.9	25.5	17.4	6.79	2.31	2.94x	-0.009	—
NC.NGVB	11.1	680	680	HNE	0.1105	0.1071	0.4020	12.9	12.0	17.3	5.48	4.12	1.33x	-1.323	—
CE.68294	11.5	375	375	HNE	0.4660	0.3903	0.3675	17.4	17.4	25.7	2.71	6.88	0.39x	+0.060	—
NC.N019B	12.3	685	685	HNE	0.3429	0.3349	0.3383	62.1	62.7	13.0	22.52	3.33	6.76x	-0.010	Unkn
NP.1765	12.8	325	325	HNE	0.4507	0.4268	0.2941	86.9	92.4	23.8	32.30	7.12	4.54x	+0.372	—
NP.1759	12.9	450	450	HNE	0.3455	0.3225	0.3088	17.1	20.9	15.3	1.90	4.98	0.38x	+0.043	—
NC.NSP	13.4	674	674	HNE	0.0545	0.0506	0.3010	7.8	10.1	19.3	4.28	3.31	1.29x	-1.784	—
NC.NTO	14.4	279	279	HNE	0.0381	0.0374	0.3109	6.1	5.7	42.9	1.30	10.89	0.12x	-2.117	Outl
NC.N002	15.4	274	274	HNE	0.0930	0.0922	0.2864	6.7	6.8	25.5	2.15	6.68	0.32x	-1.133	—
NP.1829	15.4	357	357	HNE	0.1427	0.1438	0.3043	24.9	18.9	22.0	7.70	5.05	1.53x	-0.750	—
NC.NMI	16.2	377	377	HNE	0.3774	0.3594	0.3083	19.0	18.9	16.5	1.12	5.68	0.20x	+0.153	—
NC.NLH	17.6	452	452	HNE	0.0939	0.0926	0.2795	7.0	6.8	19.2	1.33	5.38	0.25x	-1.104	—
BK.CVS	19.3	692	692	HNE	0.1230	0.1208	0.1757	18.5	17.7	8.2	8.66	2.82	3.07x	-0.374	—
NC.C032	19.9	464	464	HNE	0.1401	0.1395	0.2087	7.9	7.5	13.4	0.99	5.02	0.20x	-0.403	—
NP.1813	20.4	422	422	HNE	0.1230	0.1265	0.2409	7.8	8.3	12.7	0.93	4.88	0.19x	-0.644	—
NC.NBRB	21.5	624	624	HNE	0.0438	0.0414	0.1724	10.6	9.6	9.7	5.74	2.53	2.27x	-1.427	—
NC.N013	22.8	693	693	HNE	0.0873	0.0850	0.1357	6.5	6.3	7.6	3.67	2.39	1.54x	-0.468	—
CE.68367	23.9	373	373	HNE	0.0740	0.0738	0.1708	5.1	4.9	10.2	0.89	4.63	0.19x	-0.839	—
NC.N003	24.2	667	667	HNE	0.0172	0.0162	0.1757	1.7	1.6	13.1	1.06	3.42	0.31x	-2.384	—
NC.C040	25.0	442	442	HNE	0.0628	0.0625	0.1482	5.3	4.1	11.8	1.23	5.00	0.25x	-0.864	—
NP.1848	25.1	414	414	HNE	0.0038	0.1489	0.1701	1.1	9.6	12.7	3.94	3.64	1.08x	-0.133	Outl
CE.68433	25.2	312	312	HNE	0.0429	0.0431	0.1746	2.8	3.3	21.2	0.94	6.39	0.15x	-1.398	—
NC.NAPC	25.5	520	520	HNE	0.1159	0.1141	0.1298	21.6	19.3	7.2	10.07	2.79	3.61x	-0.129	—
NC.NHF	26.0	514	514	HNE	0.0395	0.0372	0.1428	1.9	1.8	12.8	0.51	3.32	0.15x	-1.345	—
NC.N014	26.2	324	324	HNE	0.0877	0.0872	0.1741	7.2	7.3	10.8	2.87	2.80	1.03x	-0.691	—
CE.58368	26.3	383	383	HNE	0.2029	0.2022	0.2077	12.1	12.0	15.5	0.97	4.47	0.22x	-0.027	—
CE.58558	26.4	443	443	HNE	0.0285	0.0283	0.1866	2.3	2.9	12.7	0.90	4.42	0.20x	-1.888	—
NC.CPI	26.5	436	436	HNE	0.0655	0.0637	0.1591	5.6	5.2	9.2	1.18	3.85	0.31x	-0.915	—
NC.C067	26.7	441	441	HNE	0.0598	0.0594	0.1529	3.8	3.6	10.9	0.82	4.11	0.20x	-0.946	—
NP.1847	27.4	303	303	HNE	0.1005	0.0992	0.1832	8.7	9.1	12.2	1.15	4.03	0.29x	-0.613	—
NC.NSM	27.6	698	698	HNE	0.0717	0.1415	0.1161	9.8	19.4	6.1	5.30	1.96	2.70x	+0.199	—
NC.NCC	27.6	706	706	HNE	0.0148	0.0136	0.1093	1.0	1.0	6.3	0.39	1.89	0.21x	-2.083	—
CE.58408	28.4	255	255	HNE	0.0169	0.0168	0.1608	1.8	1.9	19.4	0.55	6.54	0.08x	-2.258	Outl
NP.1768	28.4	325	325	HNE	0.0019	0.0532	0.1515	0.5	4.6	10.0	1.77	2.56	0.69x	-1.047	Outl
NC.CSPB	28.7	447	447	HNE	0.0288	0.0285	0.1654	3.8	3.8	9.5	1.07	4.10	0.26x	-1.759	—
NP.1823	30.0	479	479	HNE	0.0767	0.0747	0.1148	6.0	5.4	7.6	0.70	2.46	0.28x	-0.429	—
CE.58421	30.1	241	241	HNE	0.0234	0.0233	0.1630	2.3	2.3	15.9	0.49	5.65	0.09x	-1.947	—

ShakeMap = amplitudes the seismic network reported in stationlist.json. obspy = the same recordings fetched from FDSN and processed here. BBP = simulated. The first two should agree closely; where they do not, the ShakeMap quality flags usually explain why.
PGD is the animation pipeline's own number on both sides, read from the displacement each side hands to Blender — a different processing chain from the PGA and PGV columns, and from each other. See the displacement pages at the end.

Cross-check — how far apart are the two ‘observed’ sources?

The amplitudes the network reported in ShakeMap against the same recordings re-fetched and processed here. These should agree closely; where they do not, the ShakeMap quality flags usually explain why. A systematic offset here would be a processing fault, not physics.

Observed amplitude cross-check versus distance

Residual against distance

A trend with distance points at the attenuation model rather than the source: the simulation losing energy faster or slower than the real crust does.

Residual versus distance at four periods

Response spectra, station by station

Observed and simulated response spectra at every compared station.

Per-station detail

Nearest first. Open a station for its three-component waveform overlay and the displacement record that drives the shaking animations. Figures load when opened.

NC.NHC 4.0 km PGA obs 0.3920 g · sim 0.4443 g ln(obs/sim) -0.125

Observed versus simulated acceleration at NC.NHC

CE.68150 6.9 km PGA obs 0.3700 g · sim 0.3915 g ln(obs/sim) -0.056

Observed versus simulated acceleration at CE.68150

NC.N016 9.6 km PGA obs 0.6101 g · sim 0.3858 g ln(obs/sim) +0.458

Observed versus simulated acceleration at NC.N016

YK.KRE 10.1 km PGA obs 0.3491 g · sim 0.3521 g ln(obs/sim) -0.009

Observed versus simulated acceleration at YK.KRE

NC.NGVB 11.1 km PGA obs 0.1071 g · sim 0.4020 g ln(obs/sim) -1.323

Observed versus simulated acceleration at NC.NGVB

CE.68294 11.5 km PGA obs 0.3903 g · sim 0.3675 g ln(obs/sim) +0.060

Observed versus simulated acceleration at CE.68294

NC.N019B 12.3 km PGA obs 0.3349 g · sim 0.3383 g ln(obs/sim) -0.010

Observed versus simulated acceleration at NC.N019B

NP.1765 12.8 km PGA obs 0.4268 g · sim 0.2941 g ln(obs/sim) +0.372

Observed versus simulated acceleration at NP.1765

NP.1759 12.9 km PGA obs 0.3225 g · sim 0.3088 g ln(obs/sim) +0.043

Observed versus simulated acceleration at NP.1759

NC.NSP 13.4 km PGA obs 0.0506 g · sim 0.3010 g ln(obs/sim) -1.784

Observed versus simulated acceleration at NC.NSP

NC.NTO 14.4 km PGA obs 0.0374 g · sim 0.3109 g ln(obs/sim) -2.117

Observed versus simulated acceleration at NC.NTO

NC.N002 15.4 km PGA obs 0.0922 g · sim 0.2864 g ln(obs/sim) -1.133

Observed versus simulated acceleration at NC.N002

NP.1829 15.4 km PGA obs 0.1438 g · sim 0.3043 g ln(obs/sim) -0.750

Observed versus simulated acceleration at NP.1829

NC.NMI 16.2 km PGA obs 0.3594 g · sim 0.3083 g ln(obs/sim) +0.153

Observed versus simulated acceleration at NC.NMI

NC.NLH 17.6 km PGA obs 0.0926 g · sim 0.2795 g ln(obs/sim) -1.104

Observed versus simulated acceleration at NC.NLH

BK.CVS 19.3 km PGA obs 0.1208 g · sim 0.1757 g ln(obs/sim) -0.374

Observed versus simulated acceleration at BK.CVS

NC.C032 19.9 km PGA obs 0.1395 g · sim 0.2087 g ln(obs/sim) -0.403

Observed versus simulated acceleration at NC.C032

NP.1813 20.4 km PGA obs 0.1265 g · sim 0.2409 g ln(obs/sim) -0.644

Observed versus simulated acceleration at NP.1813

NC.NBRB 21.5 km PGA obs 0.0414 g · sim 0.1724 g ln(obs/sim) -1.427

Observed versus simulated acceleration at NC.NBRB

NC.N013 22.8 km PGA obs 0.0850 g · sim 0.1357 g ln(obs/sim) -0.468

Observed versus simulated acceleration at NC.N013

CE.68367 23.9 km PGA obs 0.0738 g · sim 0.1708 g ln(obs/sim) -0.839

Observed versus simulated acceleration at CE.68367

NC.N003 24.2 km PGA obs 0.0162 g · sim 0.1757 g ln(obs/sim) -2.384

Observed versus simulated acceleration at NC.N003

NC.C040 25.0 km PGA obs 0.0625 g · sim 0.1482 g ln(obs/sim) -0.864

Observed versus simulated acceleration at NC.C040

NP.1848 25.1 km PGA obs 0.1489 g · sim 0.1701 g ln(obs/sim) -0.133

Observed versus simulated acceleration at NP.1848

CE.68433 25.2 km PGA obs 0.0431 g · sim 0.1746 g ln(obs/sim) -1.398

Observed versus simulated acceleration at CE.68433

NC.NAPC 25.5 km PGA obs 0.1141 g · sim 0.1298 g ln(obs/sim) -0.129

Observed versus simulated acceleration at NC.NAPC

NC.NHF 26.0 km PGA obs 0.0372 g · sim 0.1428 g ln(obs/sim) -1.345

Observed versus simulated acceleration at NC.NHF

NC.N014 26.2 km PGA obs 0.0872 g · sim 0.1741 g ln(obs/sim) -0.691

Observed versus simulated acceleration at NC.N014

CE.58368 26.3 km PGA obs 0.2022 g · sim 0.2077 g ln(obs/sim) -0.027

Observed versus simulated acceleration at CE.58368

CE.58558 26.4 km PGA obs 0.0283 g · sim 0.1866 g ln(obs/sim) -1.888

Observed versus simulated acceleration at CE.58558

NC.CPI 26.5 km PGA obs 0.0637 g · sim 0.1591 g ln(obs/sim) -0.915

Observed versus simulated acceleration at NC.CPI

NC.C067 26.7 km PGA obs 0.0594 g · sim 0.1529 g ln(obs/sim) -0.946

Observed versus simulated acceleration at NC.C067

NP.1847 27.4 km PGA obs 0.0992 g · sim 0.1832 g ln(obs/sim) -0.613

Observed versus simulated acceleration at NP.1847

NC.NSM 27.6 km PGA obs 0.1415 g · sim 0.1161 g ln(obs/sim) +0.199

Observed versus simulated acceleration at NC.NSM

NC.NCC 27.6 km PGA obs 0.0136 g · sim 0.1093 g ln(obs/sim) -2.083

Observed versus simulated acceleration at NC.NCC

CE.58408 28.4 km PGA obs 0.0168 g · sim 0.1608 g ln(obs/sim) -2.258

Observed versus simulated acceleration at CE.58408

NP.1768 28.4 km PGA obs 0.0532 g · sim 0.1515 g ln(obs/sim) -1.047

Observed versus simulated acceleration at NP.1768

NC.CSPB 28.7 km PGA obs 0.0285 g · sim 0.1654 g ln(obs/sim) -1.759

Observed versus simulated acceleration at NC.CSPB

NP.1823 30.0 km PGA obs 0.0747 g · sim 0.1148 g ln(obs/sim) -0.429

Observed versus simulated acceleration at NP.1823

CE.58421 30.1 km PGA obs 0.0233 g · sim 0.1630 g ln(obs/sim) -1.947

Observed versus simulated acceleration at CE.58421

Provenance

Simulation

produced by: BBP simulated
BBP job id: job_7b20ecd07ce6408394a3
BBP version: 22.4.0
method: GP
realizations: 1 of 1 succeeded — a single stochastic rupture, not an ensemble; the bias below is one draw
realization used: r0001
sites in job spec: —
job submitted: 2026-08-04T20:16:14Z
per-site Vs30 from: submit-time record (/app/plots/gof_work/nc72282711/compare/station_specs.json)

Source parameters

magnitude used: —
hypocentre: —
depth: —
strike / dip / rake: —
mechanism source: USGS moment tensor, nodal plane 1 — the conjugate plane is equally consistent with the tensor and gives different amplitudes

Velocity model

region used: NoCal500
native for this location: Mojave500 — not installed, so the run is approximate. LABasin500 carries a deep sedimentary basin that Ridgecrest does not have, which would amplify 0.3-1 s motion.
calibration: M6.02 against GP's ~M5.5 floor
platform: arm64 under emulation — amplitudes are not SCEC-reference-accurate; this number measures BBP plus Rosetta and cannot separate them

Observed data and processing

Station selection

search radius: 100.0 km
policy: all usable within radius
stations on event: 966
without FDSN code: 0 — cannot be queried at all
candidates: 532
usable records: 349 (183 returned no usable 3-component set)
in this report: 40 with both observed and simulated
distance range: 4.0 – 30.1 km

Instrumentation

channel priority: HN?, EN?, HH?, BH?, EH?
channels used: EN, HN
data centres: EARTHSCOPE, NCEDC, SCEDC
mixed instrument types: yes — strong-motion and broadband are both present, which puts a second variable into the residual
Vs30 source: ShakeMap stationlist (per-station)

Signal processing

window: origin −60.0 s to +300.0 s (requested)
records not starting as requested: 30 of 40 — triggered instruments whose data begins later. Each trace's true start is measured and used; assuming the requested lead would misplace them.
response removal: to acceleration and velocity separately, pre-filter (0.05, 0.1, 20.0, 25.0) Hz
resampled to: 100.0 Hz
time origin: t = 0 is the rupture origin for both observed and simulated traces on every overlay

How to read this report

The metric

definition: ln(observed / simulated) RotD50 spectral acceleration, averaged across stations at each period.
sign: POSITIVE means the simulation under-predicts — real shaking was larger. NEGATIVE means it over-predicts.
scale: It is a log ratio: ±0.10 is about ±10%, ±0.69 is a factor of 2, ±1.10 is a factor of 3.
sigma: The station-to-station spread around that average. A large sigma with a small bias means the model is right on average and wrong site by site.

Reading the pattern

short-period poor, long-period good: Points at high-frequency attenuation or near-surface site response rather than the source.
long-period poor, short-period good: Points at the source — corner frequency, stress drop — or at basin response in the velocity model.
one station far off: Usually 3D site or directivity effects that a 1D layered velocity model cannot reproduce by construction. Check whether it is driving the sigma before treating it as model error.

What this does not tell you

: A pass means the simulation is consistent with recordings at these stations, for this event, under this velocity model, on this hardware. It is not a general statement about BBP, and it is not a prediction of accuracy at an unrecorded site.