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Constraints on locations of large intraplate earthquakes in the Northern Territory, Australia from observations at the Warramunga seismic array
Author(s) -
Bowman J. Roger
Publication year - 1988
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl015i013p01475
Subject(s) - geology , seismology , intraplate earthquake , fault scarp , fault (geology) , aftershock , magnitude (astronomy) , thrust fault , seismic gap , precambrian , tectonics , paleontology , physics , astronomy
Three earthquakes of M s 6.3, 6.4 and 6.7 near Tennant Creek, Northern Territory, Australia on January 22, 1988 produced 35 km of surface rupture in the Precambrian shield. The surface deformation consists of low‐angle (20°‐30°) thrust faulting on 2 main scarps separated by a 7 km gap. The Kunayungku (western) fault and the eastern end of the Lake Surprise (eastern) fault dip to the south, while the western end of the Lake Surprise fault dips to the north. Although these earthquakes are among the largest ever recorded on the Australian continent, there is no record of earthquakes larger than magnitude 5 within 500 km prior to 1987. Data from the Warramunga (WRA) seismic array located 30 km east of the rupture show no local activity between 1965 and 1986. Two small events in the fault area were observed in February, 1986 and were followed by a series of 6 m b 4 to 5.2 earthquakes in January, 1987 and their aftershocks. The 1986, 1987 and January 22, 1988 mainshocks all nucleated within a zone about 5 km across from north to south, but elongated radially away from WRA by up to 30 km. Although the distribution of these events is in the direction of poorest hypocentral resolution, we can place meaningful constraints on the epicenters by examining the range of solutions that fit the P arrival time data. The 1986 and largest 1987 events were restricted to the western part of the fault zone. The three mainshocks progressed from west to east suggesting that the Kunayungku scarp was produced by the first mainshock, and the west and east ends of the Lake Surprise scarp by the second and third, respectively.