DIEPENBEEK
Earthquake20 September 1987
- Magnitude
- 1.9ML
- Depth
- 17.7km ± 1.4
- Belgian time
- 22:07:501987-09-20
- UTC
- 20:07:501987-09-20
Main parameters
| Date and time | 1987-09-20 20:07:50 UTC 1987-09-20 22:07:50 Belgian time |
|---|---|
| Magnitude | ML 1.9 |
| Epicentral coordinates | 50.959° N, 5.537° E Uncertainty ± 1.6 km |
| Depth of hypocenter | 17.7 ± 1.4 km |
| Event ID | ROB 786 |
Data source : ROB (Royal Observatory of Belgium)
Last update : 2011-06-27 18:19:24 Belgian time
Location map
- Epicentre
- Station that recorded the event
Seismic activity in the area
Known earthquakes around the epicentre, from the catalogue of the Royal Observatory of Belgium.
Within 10 km of the epicentre
17 other earthquakes in the catalogue since 1925. 10 of them occurred after this one.
Latest earthquakes before this one
| Date | Place | Magnitude | Intensity | Distance km |
|---|---|---|---|---|
| 1987-01-21 | HOUTHALEN | ML 1.7 | – | 7.0 |
| 1986-10-27 | GENK | ML 2.0 | – | 5.6 |
| 1986-07-28 | MEEUWEN-GRUITRODE (BE) | – | – | 8.1 |
| 1970-01-10 | BILZEN | ML 3.4 | 5 | 10.0 |
| 1963-03-10 | GENK-AS | ML 3.5 | 5 | 1.3 |
Largest known earthquakes
| Date | Place | Magnitude | Intensity | Distance km |
|---|---|---|---|---|
| 1925-02-23 | BILZEN | ML 4.1 | 6 | 8.9 |
| 1963-03-10 | GENK-AS | ML 3.5 | 5 | 1.3 |
| 1970-01-10 | BILZEN | ML 3.4 | 5 | 10.0 |
| 2009-08-05 | ZUTENDAAL (BE) | ML 2.7 | 4 | 5.2 |
| 2026-10-17 | GENK (BE) | ML 2.1 | – | 3.1 |
Municipality of Genk
6 other earthquakes in the catalogue since 1963. 3 of them occurred after this one. By magnitude, it is the 4th largest of the 7 earthquakes of known magnitude in the municipality.
Latest earthquakes before this one
Notes and method
Tectonic and induced earthquakes from the Observatory’s catalogue, suspected ones included; quarry blasts, explosions and other events are not counted. Epicentral distances on the WGS84 ellipsoid.
Municipality: 2025 municipal boundaries (Statbel), applied to every earthquake, including those before the merger of municipalities. For an epicentre outside Belgium, only the circular area is given. Each earthquake’s name is the catalogue’s: it may refer to a place near the epicentre.
Magnitude: the one given on each earthquake’s page (ML preferably, otherwise MW or MS); magnitudes of different types are compared as they are.
The epicentres of historical earthquakes are only known to within a few kilometres, sometimes more: whether they fall in the area is indicative. Small earthquakes have only been recorded as the station network grew: the area’s older earthquakes are mostly the largest ones, and recent activity looks more frequent.
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
- 14
- Epicentral distance
- 20.2 – 150.6km
- Mean velocity, P wave
- 6.1km/s
- Mean velocity, S wave
- 3.6km/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. Hypocenter at a depth of 17.7 km. P wave: 9 measurements, root-mean-square deviation 0.21 s. S wave: 9 measurements, root-mean-square deviation 0.20 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.
Station measurements
P- and S-wave arrivals and ground displacement measured at each station. Click a column heading to change the order.
| km | ° | UTC | UTC | s | |
|---|---|---|---|---|---|
| Belgian seismic network (Royal Observatory of Belgium)8 stations | |||||
| MEMSMembach | 51.3 | 139 | 20:07:59.14+9.14 s | 20:08:05.35+15.35 s | 6.21 |
| ROBRobertville | 69.3 | 144 | – | 20:08:10.27+20.27 s | – |
| SNFSeneffe | 101.6 | 241 | 20:08:06.72+16.72 s | 20:08:18.50+28.50 s | 11.78 |
| AULAulne | 107.7 | 233 | 20:08:08.09+18.09 s | – | – |
| DOUDourbes | 117.1 | 215 | 20:08:09.50+19.50 s | 20:08:23.50+33.50 s | 14.00 |
| LESLessines | 122.5 | 258 | 20:08:10.05+20.05 s | 20:08:23.11+33.11 s | 13.06 |
| BOUBougnies | 129.2 | 241 | 20:08:11.56+21.56 s | – | – |
| WLFWalferdange | 150.6 | 163 | 20:08:16.00+26.00 s | – | – |
| Bensberg seismic network (University of Cologne, Germany)3 stations | |||||
| KLLKalltalsperre | 64.7 | 122 | 20:08:01.25+11.25 s | 20:08:09.00+19.00 s | 7.75 |
| STBSteinbachtalsperre | 100.5 | 113 | 20:08:07.00+17.00 s | – | – |
| BNSBensberg | 115.1 | 89 | – | 20:08:22.50+32.50 s | – |
| Dutch seismic network (KNMI)2 stations | |||||
| VKBValkenburg | 20.2 | 120 | 20:07:54.20+4.20 s | 20:07:57.70+7.70 s | 3.50 |
| ENNEPEN (Intl) | 34.6 | 128 | 20:07:56.40+6.40 s | 20:08:01.20+11.20 s | 4.80 |
| Network JCK1 station | |||||
| GSHGrosshau | 64.3 | 112 | 20:08:01.40+11.40 s | 20:08:08.90+18.90 s | 7.50 |