Geoscience Reference
In-Depth Information
13
Conclusions
PRADEEP TALWANI
This topic presents the results of studies of intraplate earthquakes in eight diverse regions
of the world (Chapters 2 to 9). Together they present an opportunity to confirm or modify
our current ideas and to devise future studies aimed at improving our understanding of
this phenomenon. These chapters primarily address the spatial and temporal pattern of
intraplate earthquakes and, where possible, identify the seismic sources. In some cases the
authors speculate on the mechanisms responsible for the seismicity. Chapter 10 confirms
our understanding on how stresses originating at plate boundaries are responsible for
mid-plate earthquakes. The unified model for intraplate earthquakes (Chapter 11) presents
a synthesis of earlier models into a testable one, while Chapter 12 on seismic hazards
cautions against the continued use of probabilistic seismic hazard analysis methodology
for intraplate earthquakes in Central and Eastern United States.
Detailed seismic tomography studies along the eastern shore of the Sea of Japan and
near the source zone of the 2001 Bhuj earthquake in India show that, with detailed data
and improved analytical techniques, it is possible to delineate the structural features of the
seismic zones and test our ideas and models of the genesis of these earthquakes and to
formulate new approaches. For most seismic zones, such detailed information is lacking.
The results of investigations presented here also help to raise questions about the validity
of our current methods of investigation and illuminate the need to develop new ones. This
chapter is divided into three parts that address the current ideas that have been confirmed
by the results of these studies; those that have been contradicted and what new insights
have been gained; and suggestions for future studies.
13.1 Observations that support earlier ideas
Sykes ( 1978 ) first suggested that there is a global pattern of intraplate earthquakes. Sub-
sequently, several investigators recognized that intraplate earthquakes preferentially occur
in old rift structures and along craton boundaries (Mooney et al ., 2012 ) . The various
examples presented in this topic have confirmed these ideas. Ziegler ( 1987 ) and Zoback
 
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