Based on some formulae for estimating ambient shear stress τ

0

which are deduced by Chen Pei-shan et al

we have studied the constants of formulae by using 161 earthquakes（M

L

2.5-5.2） occurring in Guangdong and its adjacent area recorded by Guangdong Digital Telemetry Seismogragh Network.Supposing that the level of ambient shear stress field of Guangdong area is 5 MPa

we get: C

3

=-5.707

C

4

=4.678

C

5

=-0.259?C

6

=-5.91?C

7

=-12.01.where C

3

C

4

C

5

C

6

C

7

represent the constants of some formula estimating ambient shear stress respectively by the seismic radiated energy E

the corner frequency f

c

the peak acceleration a

p

the peak velocity v

p

and the peak displacement d

p

.Comparisons are made of the constants for different areas

and it is found that the constan

ts C

4

～C

7

are roughly identical respectively for different areas

but the constant C

3

differ significantly.