… · … · Reviewed
31 km au N de Safotulafai
Fa'asaleleaga, Samoa
Magnitude
- < 3
- 3–4.9
- 5–5.9
- 6+
Distance
—
Shaking
—
Turn on your location to time the wave.
Profondeur
13 km
shallow
Aftershocks in this sequence
0
50 km · 7 d
Lat / Lon
-13.409, -172.069
UTC 03:36:29
House
ChangeEstimate
What it felt like where you live
Turn on GPS or save a zone to estimate arrival and intensity where you are. The epicenter can still be estimated.
Almost everyone feels it. Loose objects may shift.
- I
- II
- III
- IV
- V
- VI
- VII
- VIII
- IX
- X
Felt by nearly everyone. Small unstable objects fall.
What to do now
- Drop.
- Cover under a sturdy table.
- Hold on until it stops.
- Stay away from windows.
Did you feel it?
The form asks how it felt and, if there was any, the damage. That report feeds the community intensity map.
Say how it feltWhat the magnitude means
Published magnitude: 5.1 MB.
Where this earthquake sits
The energy comparison needs moment magnitude (Mw).
This is body-wave magnitude (mb), used for distant earthquakes. We do not convert it to joules; that energy needs Mw.
Intensity: the epicenter and where you live
Turn on GPS or save a zone to estimate arrival and intensity where you are. The epicenter can still be estimated.
What should I do now?
What happened
Magnitude 5.1 earthquake, 31 km au N de Safotulafai (Fa'asaleleaga, Samoa), 13 km deep. It happened il y a 2 heures (…).
Turn on your location to see how it may have felt where you are.
What to do
- 1If it is still shaking: drop, cover and hold on.
- 2Check everyone is okay and put on shoes.
- 3Small aftershocks may follow. That's normal.
- 4Text your family instead of calling.
Aftershocks: they may occur over the next 7 days within about 50 km. Nobody can predict them.
Emergency numbers in Samoa
We do not have a verified number for this country.
Call emergency services only for a life-threatening emergency or trapped people. To tell your family, send a message.
From a mobile phone, 112 works in many countries even without credit.
The main quake and its aftershocks
Aftershocks in this sequence
0No aftershocks recorded yet. If any appear, they show up here right away.
Other quakes in the area
0No earthquakes recorded in this area in the last 7 days.
How long it took to reach you
Turn on your location to time the wave.
Why it shakes here
13 km deep. Without your location we do not estimate how it felt where you are.
Technical detail
Turn on GPS or save a zone to estimate arrival and intensity where you are. The epicenter can still be estimated.
Intensity where you are
Atkinson & Wald (2007) intensity prediction equation, California coefficients (Table 1). D is the catalog hypocentral distance and R = √(D² + 14²). The paper’s residual is about 0.4 MMI units. It was calibrated on California reports, not Panama. Atkinson, Worden & Wald (2014) note that it can overpredict large magnitudes at short range.
At the epicenter: V
The Mercalli scale runs to XII. This page shows I–X, the range of the equation.
Published event intensity: MMI 4.6
This is the source value (event ShakeMap or DYFI). It describes the earthquake, not your point. Your intensity is the estimate above.
Equivalent motion
PGA ≈ 57.1 cm/s² (0.058 g)
PGV ≈ 4.3 cm/s
This is not a recording of this earthquake. It is the PGA and PGV that Worden et al. (2012) associate, at the median, with that intensity, without the optional magnitude and distance residual. Scatter is about 0.35 in log10(PGA) and 0.38 in log10(PGV).
I live in a building
Floor and era are saved in this browser, under Settings.
What the magnitude means
This is body-wave magnitude (mb), used for distant earthquakes. We do not convert it to joules; that energy needs Mw.
Magnitude is one number for the earthquake. Mercalli intensity changes with place: the same event is strong nearby and weak far away. Richter is not Mercalli.
Felt by nearly everyone. Small unstable objects fall.
Shearer, P. M. (2009). Introduction to Seismology. Vp = 6,0 km/s y Vs = 3,5 km/s como velocidades constantes de corteza. Estimación, no un tiempo de viaje 3D.
Atkinson, G. M., & Wald, D. J. (2007). “Did You Feel It?” intensity and ground-motion intensity conversion equations. Seismological Research Letters, 78(3), 362–368. doi:10.1785/gssrl.78.3.362. Coeficientes de California, tabla 1.
Atkinson, G. M., Worden, C. B., & Wald, D. J. (2014). Intensity prediction equations for North America. Bulletin of the Seismological Society of America, 104(6), 3084–3093. doi:10.1785/0120140178. AW07 puede sobrestimar magnitudes grandes a poca distancia.
Worden, C. B., Gerstenberger, M. C., Rhoades, D. A., & Wald, D. J. (2012). Probabilistic relationships between ground-motion parameters and modified Mercalli intensity in California. Bulletin of the Seismological Society of America, 102(1), 204–221. doi:10.1785/0120110156. Inversión de la mediana bilineal (ShakeMap wgrw12).
Periodo del edificio ≈ 0,1 × N segundos. Regla práctica del orden de las fórmulas de periodo de marcos (Chopra; ASCE 7). No es un análisis estructural.
Brune, J. N. (1970). Tectonic stress and the spectra of seismic shear waves from earthquakes. Journal of Geophysical Research, 75(26), 4997–5009. fc = 4,9×10^6 × β × (Δσ/M0)^(1/3), con β = 3,5 km/s, Δσ = 30 bar (3 MPa) y M0 en dyn·cm. La caída de esfuerzos es un orden de magnitud de corteza (Kanamori & Anderson, 1975), no una medición de este sismo.
Escala de intensidad de Mercalli modificada, descriptores en la línea de la ficha pública del USGS. La escala llega a XII; esta ecuación se muestra entre I y X.
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