Monitoring the seismic activity of the NW-Bohemia / Vogtland earthquake swarms

WEBNET: a local seismic network monitoring the NW-Bohemia earthquake swarm activity 
  • a local seismic network for monitoring the West-Bohemian earthquake swarm activity 
  • established in 1994, still being upgraded 
  • now (year 2002) it consists of 9 digital stations NKC, KRC, LBC, SKC, KOC, LAC, STC, VAC, TRC 
  • equipment: four Lennartz PCM 5800 telemetry stations, four Mars-88 RC, one Mars-88 FD 
  • recent upgrade: Mars-88 being replaced by Nanometrics Callisto network using Orinoco Wavelan network 
  • data transmission: Internet connection between the data centre on TV tower Zelená Hora and Prague GI 
  • a common project of the Geophysical Institute and the Institute of Rock Structure and Mechanics of the Czech Academy of Sciences 
NEW
 sensitive map: 


 

Seismic activity in the whole NW-Bohemia/Vogtland region
Occurrence of microearthquakes in the swarm area is clustered in space and time. The space distribution of the epicentres is obvious from the figure showing the microearthquakes occurred in the period 1991 - 1997. The epicentres in particular epicentral zones are distinguished using different colours. 

Nový Kostel area
The Nový Kostel area dominates the recent seismicity of the whole region. The figure depicts the space-time clustering of microearthquakes in the period 1991 - 1997. It is evident the foci tend to cluster in space, and the individual swarms took place in narrow volumes. An important feature of the spatial distribution of the hypocentres is the lamella-like character of the focal belt evident form the horizontal projection (upper left). The January 1997 swarm is shown in detail. 
The picture of seismic energy release changed after occurrence of the 2000 swarm and obtaining accurate relative locations of the 1985/86 swarm. As is indicated in the figure, the major part of the ectivity takes place close to a steeply dipping almost N-S oriented fault plane. 
 
Try the 3D view of the earthquakes in the Novy Kostel area. It displays a 3-dimensional view of the hypocentres occurred in this epicentral area witihn the period 1991-2001. 
HELP: rotate the image by dragging by mouse; zoom the image by Shift+drag mouse up/down.

The animation was created using the Java applet LiveGraphics 3D by Martin Kraus and it works with IE 5.0 and later only.

January 1997 Ml 3.0 swarm
The January 1997 swarm was the best ever recorded seismic sequence in the West-Bohemia/Vogtland region thanks to the WEBNET network. It occurred in the Nový Kostel area in the period from January, 11 to January 28, 1997 when more than 1500 microearthquakes in the magnitude range from -2.0 to 3.0 were recorded. The focal area of the swarm shows a corner-like shape dipping to East. 
A combination of the waveform type analysis and full moment tensor determination enabled more than 700 events to be classified following their focal mechanism. Totally eight source mechanism types were identified differing both in their fault plane solution angles and in percentage of DC component. The figures show spatial distribution of particular event types and representative source mechanisms corresponding to eight multiplet groups. 
The occurrence of particular foci mechanisms was not random. In the first phase of the swarm the normal movements (red foci) dominated, while in the second phase the reverse events with higher volumetric components (blue foci) prevailed. The attached animation shows the temporal development of the swarm. 

The people behind WEBNET
  • Josef Horalek - head of group, source studies, signal processing 
  • Alena Bouskova - data processing 
  • Tomas Fischer - SW & network maintenance, locations, source studies, signal processing 
  • Frantisek Hampl (+1997) - founder of most of stations 
  • Milan Broz - station maintenance (Institute of Rock Structure and Mechanics) 
  • Petr Jedlicka - station & network maintenance 
  • Jiri Soukup - station & network maintenance 
  • Zuzana Hudova - data processing 
  • ... and occasional co-workers 
 
 
 
 
 
 
 
  

Send comments to Tomas Fischer

Last update  2002-10-09