Teleseismic Detection of a Slow Precursor to the Great 1989 Macquarie Ridge Earthquake

Low-frequency spectra for the 1989 Macquarie Ridge earthquake (magnitude 8.2) show an amplitude increase and a phase-delay decrease below 6 millihertz that require a short-term slow precursor. This earthquake can be modeled as a compound event in which a fast-rupturing, ordinary earthquake was initiated by an episode of slow, smooth deformation that began more than 100 seconds before the main shock. The moment released in the slow precursor was large, about 3 x 1020 newton-meters, equivalent to an event of magnitude 7.6. The data are consistent with the precursor being generated in a region of the oceanic upper mantle below the main rupture.

[1]  Gregory C. Beroza,et al.  Searching for slow and silent earthquakes using free oscillations , 1990 .

[2]  H. Kanamori,et al.  A slow earthquake , 1979 .

[3]  Eugene Herrin,et al.  Phase-matched filters: Application to the study of Rayleigh waves , 1977, Bulletin of the Seismological Society of America.

[4]  Remo Guidieri.  Res , 1995, RES: Anthropology and Aesthetics.

[5]  J. Weeks,et al.  The frictional behavior of serpentinite: Implications for aseismic creep on shallow crustal faults , 1991 .

[6]  Hiroo Kanamori,et al.  Focal process of the great Chilean earthquake May 22, 1960☆ , 1974 .

[7]  D. L. Anderson,et al.  Preliminary reference earth model , 1981 .

[8]  T. Jordan.  Far‐field detection of slow precursors to fast seismic ruptures , 1991 .

[9]  Shamita Das.  Reactivation of an oceanic fracture by the Macquarie Ridge earthquake of 1989 , 1992, Nature.

[10]  F. Gilbert,et al.  Temporal Variation of the Seismic Moment Tensor and the Evidence of Precursive Compression for Two Deep Earthquakes , 1974, Nature.

[11]  J. Nábělek,et al.  Rupture process of the MacQuarie Ridge Earthquake of May 23, 1989 , 1990 .

[12]  Alan T. Linde,et al.  Near‐field high resolution strain measurements prior to the October 18, 1989, Loma Prieta Ms 7.1 Earthquake , 1990 .

[13]  F. A. Dahlen,et al.  On the ratio of P-wave to S-wave corner frequencies for shallow earthquake sources , 1974, Bulletin of the Seismological Society of America.

[14]  Hiroo Kanamori,et al.  Mode of the strain release along the Gibbs fracture zone, Mid-Atlantic ridge , 1976 .

[15]  A. Dziewoński,et al.  Centroid-moment tensor solutions for April-June 1989 , 1990 .

[16]  H. Kanamori.  A slow seismic event recorded in Pasadena , 1989 .

[17]  B. Romanowicz,et al.  The 23 May 1989 MacQuarie Ridge Earthquake: A very broad band analysis , 1990 .

[18]  J. Weeks,et al.  Frictional behavior of granite at low and high sliding velocities , 1987 .

[19]  J. Weeks,et al.  Two‐mechanism model for frictional sliding of serpentinite , 1992 .

[20]  Thomas H. Jordan,et al.  Generalized seismological data functionals , 1992 .

[21]  E. Okal,et al.  Slow earthquakes along oceanic fracture zones: evidence for asthenospheric flow away from hotspots? , 1982 .

[22]  J. Mills,et al.  Residual dispersion measurement—a new method of surface-wave analysis , 1972, Bulletin of the Seismological Society of America.

[23]  Jeffrey Park.  Radial mode observations from the 5/23/89 MacQuarie Ridge Earthquake , 1990 .

[24]  F. Dahlen.  Multiplet coupling and the calculation of synthetic long-period seismograms , 1987 .

[25]  Mark A. Riedesel,et al.  Display and assessment of seismic moment tensors , 1989 .

[26]  Hiroo Kanamori,et al.  Use of long-period surface waves for rapid determination of earthquake-source parameters , 1981 .

[27]  T. Tullis.  Rock friction constitutive behavior from laboratory experiments and its implications for an earthquake prediction field monitoring program , 1988 .

[28]  J. Arthur Snoke,et al.  Slow earthquakes and stress redistribution , 1978, Nature.

[29]  Jeffrey Park.  Asymptotic coupled-mode expressions for multiplet amplitude anomalies and frequency shifts on an aspherical earth , 1987 .

[30]  T. Jordan,et al.  Moment‐tensor spectra of the 19 Sept 85 and 21 Sept 85 Michoacan, Mexico, earthquakes , 1986 .

[31]  P. Silver,et al.  Low‐frequency source characteristics of the great 1960 Chilean earthquake , 1989 .

[32]  A. Prozorov,et al.  Study of the properties of seismicity in the Mexico region , 1984 .

[33]  L. Ruff.  The Great MacQuarie Ridge Earthquake of 1989: Introduction , 1990 .

[34]  T. Jordan,et al.  Optimal estimation of scalar seismic moment , 1982 .