Geoscience Reference
In-Depth Information
Passive
Rift
Archean Craton
Interior
Rift
Passive
Rift
M
M
100
100
200
200
300
300
400
400
Adapted from Mooney et al. , 2012
0
500
1000
km
Figure 11.2 A schematic continental lithospheric cross-section. The primary locations of seismicity
(solid arrows) are in rifts located along the passive margins and continental interior, and at the
boundary of the deep Archean craton with the surrounding regions. The shaded area shows the
chapter I will focus on the larger earthquakes (M
4, 5) with rift association, realizing
that nearly 40% of M
percentage of smaller events may have other causes.
According to my hypothesis, large IPEs occur by reactivation of faults in the present-
day compressional stress field. Whether a fault within a rift will be reactivated depends on
whether or not it is favorably oriented relative to S
T
, its strength, its tectonic history and
geometry. An intracratonic rift forms in response to plate margin processes. The resulting
geometry is a series of half-grabens with alternating polarity along strike, separated by
accommodation zones (e.g., Ziegler, 1987).Thus, the present configuration of the rift is
the result of its tectonic history, and reactivation of structures within it depends on their
orientation with respect to S
T
. Insight into reactivation of structures within a rift by stress
inversion can be provided by modeling, which is described next.
11.8 Insights from basin inversion modeling
The term “basin inversion” is used to describe the tectonic process in which deep parts
of a sedimentary basin or continental rift reverses its vertical direction of movement and
elongate structure that has deformed in response to compression. Among different intraplate
discontinuities within the rigid crust, rifts with a thinner crust are most prone to inversion
in response to compressional stresses emanating from plate boundaries (Ziegler, 1987).
Ziegler described many examples of these inversion zones in central Europe and speculated
on their genesis. To investigate the mechanism of these inversion zones, Nielsen and Hansen
compressional intraplate stress field. The results of their model showed that a pre-existing
