Body-wave Magnitude
3.9
mb · live
S − P Time
13.7
seconds
Computed Distance
150
km from S − P
Z First Motion (P)
↑ Compressional
all-azimuth up
P Arrival (model)
18.6
s after origin
S Arrival (model)
32.3
s after origin
Focal Mechanism
Compressional (↑)
Dilatational (↓)
Station take-off
Source-to-Station Cross Section
t = 0.0 s
P ray (compressional, ~7 km/s)
S ray (shear, ~4 km/s)
Hypocenter
Broadband station
Interpretation
An underwater explosion radiates compressional energy almost isotropically. The first motion on the vertical channel is uniformly up (compressional) at all azimuths, and the S-wave amplitude is markedly smaller than the P-wave. The focal-mechanism beach ball is a single solid compressive quadrant. This is the diagnostic signature of an explosive source — and it is visible on a single three-component broadband station within minutes of the event, without ever asking who set the charge.
Keyboard
- Space Play / Pause
- ← → Scrub time ±1s
- R Reset
- C Compare mode
- 1–6 Select source
- H High contrast
- E Copy report