What are the differences of focal parameters between earthquakes in volcanic region and other region? A network with 15 sets of EADS-3M mobile digital seismic recorders were set up in Tengchong volcanic region from 2002-06-13 to 2002-09-13. More than 400 earthquakes in this region and adjacent areas were recorded. 33 records were selected to calculate focal dynamic parameters in Tengchong volcanic region by spectrum analysis method. Result calculated from S-wave is used to discuss varied time-spatial-intensity parameters. The earthquake in Tengchong is shallow earthquake with smaller magnitude. Scalar seismic moment in Tengchong is varied between 8.32E10 and 8.96E12 N·m. The relation between scalar seismic moment and local magnitude in Tengchong is logM

0

=0.98M

L

+1048 which is esentially identical to logM

0

=0.99M

L

+1043 in adjoined Yao’an tectonic area. Focal dislocati

on is in the range of 0.124 km to 0.418 km in Tengchong region. The stress drop is in the range of 0.005 MPa to 0.277 MPa. The value at most is only one-fifth of 0.021 MPa

1

9.4 MPa in Yao’an tectonic area. This might be the answer to the above question. The results also show the magma activity and derivational earthquake in shallow crust in Tengchong volcanic region. Lower crust stress here show lower stress accumulation.