Probabilistic earthquake risk maps of southwest Western Australia
Dataset Identification:
Resource Abstract:
New earthquake risk maps of southwest Western Australia including continental margins have been prepared. The risk is depicted
as contours of peak ground velocity, acceleration, and ground intensity with a 10 per cent probability of being exceeded in
50 years. The maps are based on the Cornell-McGuire methodology. Ten earthquake source zones have been thus defined and corresponding
recurrence relations derived. The relation obtained, using a maximum-likelihood fit, for the primary zone to the east of Perth,
is log N = 3.66-0.90 ML, where N is the number of events greater than or equal to the Richter magnitude, ML. Local intensity
attenuation constants, a, b, and c, are derived for the expression I = aebMLR-c, where I is the estimated Modified Mercalli
intensity at a hypocentral distance R km from an earthquake of magnitude ML. Using the relation log A= I/3.1-2.3 to convert
the intensity to peak ground acceleration, A in m.s-2, the adopted constants were 0.025, 1.10 and 1.03 respectively. Similarly,
using the empirical formula 21 = 7v/5 to convert intensity to peak ground velocity, v in mm.s-1, the corresponding values
were 3.30, 1.04 and 0.96, respectively. The contour expressing the greatest risk in the area of interest is that of a peak
ground velocity of 160 mm.s-1, and it encloses an area of about 2000 km2 centred on the most active source zone east of Perth.
The value for Perth city is 48 mm.s-1. Increasing (i) the maximum magnitude from ML 7.5 to ML 8.5; (ii) the depth of earthquake
foci from 5 km to 15 km; (iii) the b value from 0.90 to 0.94; and (iv) the attenuation constants to their estimated maximum
value, in the primary source zone, changes the Perth velocity contour from 48 mm.s-1 to 56 mm.s-1 , 48 mm.s-1 , 42 mm.s-1
, and 58 mm.s-1, respectively. The omission of a suspected seismic gap 100 km east of Perth from the primary source zone changes
the velocity contour from 48 mm.s-1 to 46 mm.s-1. Sensitivity to adopting another empirical relation between peak ground acceleration
and intensity has been examined. This increases the risk at Perth from 0.44 m.s-2 to 0.65 m.s-2. We recommend a microzonation
study of Perth and installation of more strong-motion instruments to improve our risk estimates, which should be updated in
5-10 years.
Citation
Title Probabilistic earthquake risk maps of southwest Western Australia
publication Date
1987-01-01T00:00:00
Series
Name BMR Journal of Australian Geology and Geophysics
Issue 10:2:145-151
cited responsible party
-
publisher
organisation Name
Bureau of Mineral Resources, Geology and Geophysics
Metadata standard for this record:
ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
standard version:
1.1
Metadata record identifier:
fae9173a-709b-71e4-e044-00144fdd4fa6
Metadata record format is ISO19139-2 XML (MI_Metadata)