Citation

Geoscience Australia provides most of its products for free under a Creative Commons Attribution 4.0 International Licence. We only require that you reference the use of our data or information using the following citation:
Michael-Leiba, M.O., 1987. Temporal variation in seismicity of the Southwest Seismic Zone, Western Australia: implications for earthquake risk assessment. BMR Journal of Australian Geology and Geophysics  10:2:133-137. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

Abstract

In the area 30-33°S, 116-118°E of the Southwest Seismic Zone of Western Australia, ML -4.0 earthquakes for the period 1960-1983 do not fit a Poisson model. However, when foreshocks and aftershocks are excluded, the hypothesis of a Poisson distribution cannot be rejected for the resulting series of main shocks. A similar result holds for the subset of ML -5.0 events for the period 1949- 1983. Consequently, when earthquake risk is being assessed by methods that assume a Poisson distribution, foreshocks and aftershocks should be excluded . However, the consequent apparent reduction of risk caused by removing these potentially damaging earthquakes should be pointed out. Although records of seismicity are probably incomplete for the early part of this century, there appears to have been an increase in numbers of ML -4.0 events, starting around 1949. Although, the data are too uncertain to test the increase in the ML -4.0 main shocks statistically, there has been an approximate five-fold increase in the mean yearly number of ML -4.5 main shocks during the period 1949 to 1983, compared with the period 1923 to 1948. This is clearly larger than would be expected from a Poisson process. Consequently, the apparent increase in the number of ML -4.0 events is probably also real and not an artefact of a Poisson process. Also, there were no ML -5.0 events during the period 1923 to 1948, and the only two ML -6.0 earthquakes this century took place in 1968 and 1979. This increase in seismicity since the late 1940s should be taken into account in the interpretation of earthquake risk calculations.
Google map showing geographic bounding box with values North bound -27.6 East bound 120.37 West bound 115.1 South bound -33.55
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Product Type/Sub Type

nonGeographicDataset - GA Publication - Journal

Constraints

license
Creative Commons Attribution 4.0 International Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1987

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Journal
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-27.6
East bound
120.37
West bound
115.1
South bound
-33.55

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Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

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distributor
Organisation Name
Geoscience Australia
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Canberra
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Country
Australia
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Metadata File Identifier

fae9173a-7098-71e4-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2015-03-23

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

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pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact Geoscience Australia Client Services via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).