DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

efractory
refractory Material that resists heat, or in geology,
elements or compounds with high melting
or dissociation temperatures that remain in
formations even after heating. See volatile.
region of anomalous seismic intensity A region
where seismic intensity becomes markedly
intense for the magnitude of an earthquake or for
the epicentral distance. For instance, there are
many cases showing that the Pacific coast from
Hokkaido to Kanto districts in Japan is a region
of anomalous seismic intensity for deep earthquakes
beneath the Japan Sea and shallow earthquakes
along the Pacific coast. This is thought
to be because seismic waves, including shortperiod
components, reach the region, passing
through the subducted plate with low attenuation.
In a more typical situation, seismic waves
passing through a high attenuation region away
fromthesubductedplatedonotproducesensible
ground motion. Recent research also suggests
that the existence of a low velocity layer overlying
the subducted plate plays an important role
in producing a region of anomalous seismic intensity.
Regolith The fine powdery surface of an atmosphereless
planet (e.g., the moon) which is
produced by radiation and micrometeoric impacts
on the surface.
Regulus 1.38 magnitude star of spectral type
B7 at RA10 h 08 m 22.2 s , dec +11 ◦ 58 ′ 02 ′′ .
Reissner–Nordström (RN) metric In general
relativity, the unique, asymptotically flat
metric describing the spherically symmetric
gravitational and electric fields of an isolated
massM with electrical charge.
In spherical coordinates (t,r,θ,φ), the line
element takes the form (in geometric units with
speed of light c = 1, and Newton’s constant
G= 1)
ds 2
= − 1 − 2M
© 2001 by CRC Press LLC
394
r
+ 1 − 2M
r
Q2
+
r2
dt 2
+ Q2
r 2
−1
dr 2
2
+r dθ 2 + sin 2 θdφ 2
,
The electric field is described by a potentialφE
=Q/r.
For Q 2 >M 2 the Reissner–Nordström metric
is regular everywhere except for the real
(naked) singularity at r = 0. For Q 2 ≤M 2 ,
theReissner-Nordströmmetricdescribesablack
hole very similar to the Schwarzschild metric;
there is an inner and an outer horizon r± =
M± M 2 −Q 2 instead of just one horizon.
Outside the outer horizon r+ (i.e., for r>r+)
the solution has the expected properties of a
mass and charged spherical mass (Region I). For
r−