KERPEN (DE)

Quarry blast25 May 2021

Magnitude
1.7ML
Depth
–
Belgian time
12:45:052021-05-25
UTC
10:45:052021-05-25

Main parameters

Date and time2021-05-25 10:45:05 UTC
2021-05-25 12:45:05 Belgian time
MagnitudeML 1.7
Epicentral coordinates50.296° N, 6.716° E
Uncertainty ± 2.3 km
Event IDROB 13525

Data source : ROB (Royal Observatory of Belgium)
Last update : 2021-10-04 11:06:09 Belgian time

Location map

  • Epicentre
  • Station that recorded the event

Macroseismic inquiry

Intensities derived from the answers to the online questionnaire “Did you feel an earthquake?”, grouped by municipality (former municipalities included). The map and the chart give the intensity of each municipality.

Answers
1
Municipalities
1
Farthest municipality
2km · BERNDORF
Countries
Germany
Grouping
Show
Intensity of the municipality (CII)
  • I
  • II
  • III
  • IV
  • V
  • VI
  • VII+
Answers per municipality
  • 3–4
  • 5–9
  • 10–19
  • 20–49
  • ≥ 50
  • felt, fewer than 3 answers
  • Epicentre

Answers by intensity

IntensityAnswers
I0
II0
III1
Total1

Warning: the intensities derived from the inquiry are raw, unverified data.

Notes and method

Intensity of a municipality or a cell (CII, Community Internet Intensity) is computed as follows:

  • I if no answer reports that the earthquake was felt;
  • F earthquake felt, but fewer than 3 answers kept per municipality or cell;
  • II–IX computed from 3 answer(s) kept: CII = 3.40 ln(CWS) − 4.38 (Wald et al., 1999), applied to the weighted sum (CWS) of the mean indexes of the answers; at least II if felt, at most IX.

Answers kept (USGS method, as applied by the ROB): reliability of 80 or more, given on the ground floor up to the 4th floor (or unknown floor), without those more than two standard deviations from the mean. The “felt” index is weighted by the answer to “Did others nearby feel it?”.

Distribution by intensity: macroseismic intensity (MI) recorded for each answer.

Cells: 5 or 10 km squares of the Belgian Lambert 72 grid, each answer placed at its geocoded address or at the point it placed on the map, otherwise at the centre of its municipality. The positions of the answers are published only rounded to about 1 km, in “Arrival of the answers”. Grid cell method: Van Noten et al. (2017), Solid Earth 8, 453–477, doi:10.5194/se-8-453-2017.

Depth not determined: distances measured from the epicentre.

Answers left out, of reliability below 10 (automated submissions detected by the form, inconsistent answers or answers rejected by the analysts): 102.

Answers read on 2026-11-09 09:53.

Arrival times at the stations

Each station first records the P wave, the fastest, then the S wave. The farther a station is from the epicentre, the later the waves reach it and the wider the gap between the two.

Stations
9
Epicentral distance
48.5 – 153.1km
Mean velocity, P wave
5.5km/s
Mean velocity, S wave
3.3km/s
  • P wave
  • S wave
  • Curve fitted to the measurements
Notes and method

Curves: travel time of a direct wave in a homogeneous medium. The velocity of each wave and an origin-time shift, common to both, are fitted to the measurements by least squares. Depth not determined: hypocenter placed at the surface for the calculation. P wave: 7 measurements, root-mean-square deviation 0.19 s. S wave: 5 measurements, root-mean-square deviation 0.27 s.

Stations farther than 120 km are left out of the fit: the first waves to reach them have travelled beneath the crust, through the mantle, where they propagate faster.

Table of measurements

Station measurements

P- and S-wave arrivals and ground displacement measured at each station. Click a column heading to change the order.

km°UTCUTCs
Belgian seismic network (Royal Observatory of Belgium)8 stations
KLBKalborn48.524310:45:13.22+7.98 s10:45:19.35+14.11 s6.13
HOUHouvegnez51.027710:45:13.71+8.47 s10:45:19.41+14.17 s5.70
MRGMont Rigi51.5298–10:45:19.86+14.62 s–
VIAVianden54.522310:45:14.52+9.28 s––
MEMSMembach61.030510:45:15.27+10.03 s10:45:23.12+17.88 s7.85
MEMHMembach61.030510:45:15.67+10.43 s10:45:23.09+17.85 s7.42
LCHLa Chartreuse88.029610:45:20.51+15.27 s––
DOUDourbes153.126210:45:31.08+25.84 s10:45:49.92+44.68 s18.84
Dutch seismic network (KNMI)1 station
HGNHeimansgroeve76.231310:45:17.93+12.69 s––
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