Geoscience Reference
In-Depth Information
5.5
radius[km]
20
50
100
200
500
1000
5.0
6
4.5
5
4.0
4
3.5
3
3.0
2
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
log(Felt Area, km
2
)
m
R
(Regional)
(a)
(b)
teleseismic m
b
scale (IASPEI). Error bars are standard deviations of the mean values. Grey line is the
m
b
:m
R
regression, which is not statistically different than m
b
=
m
R
(dashed line). The regional scale
is equivalent to the teleseismic magnitude. (b) Empirical relationship between total felt area (A
f
)and
magnitude. The magnitudes used in this plot are average of m
b
and m
R
values. The grey line is the
regression
m
=
2.44
−
0.015log(A
f
)
+
0.0922[log(A
f
)]
2
; standard deviation
=
0.35 magnitude units.
The solid thin line is the empirical relation for Central and Eastern United States (Nuttli
et al
.,
1979
)
using magnitude m
b
(L
g
). The dashed line is the approximate relationship between m
b
and felt area
from the worldwide compilation of Johnston
et al
.(
1994
)
. Top axis is the equivalent radius for the
felt area.
3.2 Earthquake catalogue
The Brazilian earthquake catalogue is based mainly on the compilation of Berrocal
et al
.
(1983, 1984) complemented since 1982 by the
Brazilian Seismic Bulletin
prepared jointly
by the universities of Sao Paulo (USP), Brasılia (UnB), Rio Grande do Norte (UFRN),
and the Technological Research Institute (IPT) of the state of Sao Paulo. Other institutions
(State University of Sao Paulo, UNESP, and National Observatory, ON) also contribute
data to the Brazilian bulletin. Events in a neighbouring area just west of the Brazilian
border (also characterized as SCR) are included to help establish correlation with intraplate
geological and geophysical features - these events outside Brazil were taken from the
literature, the ISC catalogue, as well as located by the Brazilian stations (e.g., Berrocal
et al
.,
The magnitude scale adopted in the catalogue is the 1-second P-wave teleseismic m
b
,
especially for events larger than about 5, and the regional magnitude (m
R
) developed by
maximum P-wave particle velocity in the period range 0.1 to 1.0 s.
Figure 3.1a
shows that
the regional magnitude m
R
is equivalent to the teleseismic m
b
scale in the range 3.5 to 5.5.
