Port Moresby Geophysical Observatory
~ Applied Seismology
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PNG Seismotectonics and Structure |
Seismic Hazard/Risk |
Tsunami Hazard/Risk
PNG Seismotectonics and Structure
On-going seismological studies are revealing the geological
structure and dynamics of the PNG region on both large and
smaller scales. The boundaries of the lithospheric plates in
the PNG region are becoming clearer
(see tectonic boundaries figure),
although some boundaries remain uncertain. The nature of the
processes at the plate boundaries are also being revealed by
seismological studies.
On a smaller scale, a number of recent studies have shown the
value of monitoring earthquake sequences (main event and aftershocks)
which have resulted in mapping of active faults and determination
of sense of motion on the faults.
Understanding the structural controls on and tectonic setting of
mineral and hydrocarbon systems is the key to the mapping and
development of these resources. The progressive study of earthquake
sequences helps to define crustal structure both by direct evidence
on individual faults and by association between elements of fault
systems.
Dense and mobile networks of seismic stations allows detailed studies
to be made in specific areas of seismic activity. Strategic
deployment of seismic network stations assists in the elucidation
of active crustal structures. In many cases, this information will
be relevant to existing mineral and petroleum deposits which are
located in areas of young, active and evolving tectonics.
Seismic Hazard/Risk
Evaluation of seismic hazard/risk at different scales is progressing.
On a national, regional scale, studies have been conducted to
determine return periods and probabilities of occurrence of large
earthquakes. These studies have contributed to the definition of
seismic zones in PNG and to the establishment of the PNG Building
Code. The results of this work are routinely applied to areas of
specific concern such as population centres and in the vicinity of
industrial (including mining and petroleum) development projects.
The co-determination of ground accelerations provides information
vital to industry in general, but particularly to the mining and
petroleum industry, to construction/engineering companies and to
town planners.
Tsunami Hazard/Risk
Studies by PMGO have catalogued historical tsunamis in the PNG
region and defined areas of greatest tsunami vulnerability.
These studies have demonstrated that a common cause of tsunamis
is earthquakes. Because of the high speed of the waves that
constitute tsunamis, it has become clear that over the relatively
short distances of propagation of these waves within the PNG region,
tsunami warning systems that track the tsunamis themselves give
insufficient time for practical warnings. Probably the most
effective warning for earthquake-induced tsunamis is the causative
earthquake itself whose speed through the ground is much greater
than the speed of tsunamis. Thus, the maintenance of a regional
seismic network can be a very important tsunami surveillance measure.
Studies of the seismic events related to the 1998 Aitape tsunami
indicate that the threat of tsunami generation may involve not just
large shallow earthquakes but also unconsolidated, unstable sediments
in off-shore areas that are displaced by the earthquake shaking.
Related studies show that local bathymetry may amplify tsunamis.
These results can be used to help identify other areas of coastal
PNG which are vulnerable to local tsunami generation, including
project sites and population centres.