Moment tensor rate functions for the 1989 Loma Prieta Earthquake

Ruff, Larry J.; Tichelaar, Bart W.

doi:10.1029/gl017i008p01187

Cited by 31 publications

(20 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The largest aftershock (May 16, Ms = 7.7) of the 1968 event has a normal fault motion, with a slip direction almost opposite to that of the main shock. Tichelaar [1990] are in agreement with focal mechanisms from other researchers [Ichikawa, 1971;Yoshii, 1979;Honda et al , 1967;Sasatani , 1976;Stauder and MuMchin, 1976] and are consistent with underthrusting of the Pacific plate beneath Japan. We find a depth of 21-33 km for this large "backwards" aftershock, which is consistent with Kanamori Figure 4, but for the Hokkaido trench junction.…”

Section: The Hokkaido Trench Junctionsupporting

confidence: 92%

Depth of seismic coupling along subduction zones

Tichelaar¹,

Ruff²

1993

J. Geophys. Res.

Self Cite

430

315

View full text Add to dashboard Cite

Underthrusting at subduction zones can cause large earthquakes at shallow depths but it is always accommodated by aseismic deformation below a certain depth. The maximum depth of the seismically coupled zone (or seismogenic zone) is a transition from unstable to stable sliding along the plate interface. We have determined the depth of this stability transition for the circurn‐Pacific subduction zones of: Honshu, Kuriles, Kamchatka, Aleutians, Alaska, Mexico, and Chile. These subduction zones have experienced great interplate earthquakes and the aftershock regions are well‐located. Depth estimates of interplate events that are located at the downdip edge of the aftershock regions are used to determine the maximum depth of seismic coupling. For an average P wave velocity of 6.7 km s−1 above the plate interface, we find that for most subduction zones the stability transition occurs at 40 ± 5 km depth. There are, however, several exceptions. At the Hokkaido trench junction, where the Japan trench and the Kurile trench intersect, seismic coupling is deep and extends down to 52–55 km. Deep coupling was also found in the Coquimbo region in central Chile. The Mexico subduction zone has shallow coupling: the transition occurs at 20–30 km depth. Previous studies of micro‐earthquakes in Honshu, Hokkaido, the Aleutians, and Alaska show that earthquakes within the upper plate extend no deeper than the downdip edge of the coupled zone that we find. Given our measurements of seismic coupling depth, we then explore the mechanism that may determine coupling depth. The concept of critical temperature has been used to explain the depth of seismic coupling in other tectonic environments, thus we first test whether a critical temperature can explain our results. Temperatures at the plate interface are dependent on many variables; but two that are poorly determined are shear stress and radiogenic heat generation. Shear stress has been constrained by inversion of heat flow data. Assuming a crustal radiogenic heat production rate of 3.1 exp−z/8.5 μWm−3 and a constant coefficient of friction, we find two critical temperatures of about 400 ° C and 550 ° C. The lower critical temperature may be characteristic of regions with a relatively thick continental crust and the higher temperature of regions with a relatively thin continental crust. On the other hand, one single critical temperature of about 250 ° C can explain the coupling depths if shear stresses are constant with depth.

show abstract

Section: The Hokkaido Trench Junctionsupporting

confidence: 92%

Depth of seismic coupling along subduction zones

Tichelaar¹,

Ruff²

1993

J. Geophys. Res.

Self Cite

430

315

View full text Add to dashboard Cite

show abstract

“…The method that allows us to retrieve the rupture history was designed by Sileny, Campus & Panza (1992), who complemented the linear inversion with a subsequent step which reduces the independent MTRFs to the moment tensor and the STF. Alternative ways of performing this reduction were suggested by Ruff & Tichelaar (1990) and Vasco (1989).…”

Section: Introductionmentioning

confidence: 99%

Robust retrieval of a seismic point-source time function

Kravanja

Panza

Šı́lený

1999

Geophysical Journal International

View full text Add to dashboard Cite

A comparison of two waveform‐inversion methods designed to retrieve the mechanism of a seismic source and of its time function is presented using vertical‐component synthetic signals, computed for velocity with a maximum frequency of 10 Hz. The geometry of the array of recording stations simulates the northeastern Italy Seismometric Network (OGS Trieste), consisting of 16 stations of which 12 are short period, vertical component only, three are short period, three components, and one is broad band. The synthetic seismograms are inverted using an inconsistent forward modelling technique; that is, by means of Green’s functions (GFs) constructed for a structural model different from those used to generate the synthetic data. The approach based on ‘overparametrization’ of the rupture process, by means of independent moment tensor rate functions (MTRFs), and their subsequent reduction to the source time function (STF) (Method I) is shown to be superior to a traditional approach where the rupture process is constrained a priori (Method II). With Method I, the effects of inconsistent structural modelling are partially absorbed into the uncorrelated parts of the MTRFs and their reverse slips, which allows us to eliminate them by subsequent retention of the STF as their positively constrained correlated part. Method I is shown to be able to yield a reasonable estimate of the STF even in the case when the traditional approach fails completely. Inadequacy of the GF, which may occur due to mislocation of the hypocentre, is taken into account by comparing the two approaches: the source depth is optimized simultaneously with the determination of the mechanism and the source time function. In addition to its capacity to handle inaccurate structural models, the overparametrization yielding a linear inverse scheme is completely independent from the starting model of the mechanism: Method II, using a gradient scheme, can proceed properly only if the starting source parameters are sufficiently close to the true ones. The extension of the comparison of the performances between the two methods to an Md 3.0 earthquake near Friuli, in February 1988, recorded by seven stations of the OGS Trieste Network gives results in good agreement with the synthetic tests. The orientation of the nodal planes retrieved using Method I is in good agreement with the orientation of the source mechanism retrieved from the polarity of first arrivals, while Method II gives consistent results only when starting from the source parameters retrieved using Method I.

show abstract

“…In our proposed method, we adopt a wavelet-based strategy to parameterize the moment tensor rate functions (MTRFs). The MTRFs allow the timedependent source mechanism such that each moment tensor component has its own time history (Dziewonski and Gilbert, 1974;Stump and Johnson, 1977;Ruff and Tichelaar, 1990;Sileny et al, 1992). By choosing the "best" wavelet as the basis, we can construct an adaptive, problem-dependent parameterization for the MTRFs, thereby achieving accurate approximations while significantly reducing the number of parameters that need to be estimated through inversion.…”

Section: Wavelet-domain Inversion Methodsmentioning

confidence: 99%

Characterization of an Explosion Source in a Complex Medium by Modeling and Wavelet Domain Inversion

Toksoez¹

2006

View full text Add to dashboard Cite

Moment tensor rate functions for the 1989 Loma Prieta Earthquake

Cited by 31 publications

References 8 publications

Depth of seismic coupling along subduction zones

Depth of seismic coupling along subduction zones

Robust retrieval of a seismic point-source time function

Characterization of an Explosion Source in a Complex Medium by Modeling and Wavelet Domain Inversion

Contact Info

Product

Resources

About