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287
New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface
, 1994
"... Abstract Source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude (M), surface rupture length, subsurface rupture length, downdip rupture width, rupture area, and maximum and average displacement per event. The resultin ..."
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Cited by 524 (0 self)
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Abstract Source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude (M), surface rupture length, subsurface rupture length, downdip rupture width, rupture area, and maximum and average displacement per event. The resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment, moment magnitude, subsurface rupture length, downdip rupture width, and average surface displacement. Each source parameter is classified as reliable or unreliable, based on our evaluation of the accuracy of individual values. Only the reliable source parameters are used in the final analyses. In comparing source parameters, we note the following trends: (1) Generally, the length of rupture at the surface is equal to 75% of the subsurface rupture length; however, the ratio of surface rupture length to subsurface rupture length increases with magnitude; (2) the average surface displacement per event is about onehalf the maximum surface displacement per event; and (3) the average subsurface displacement on the fault plane is less
Seismic moment assessment of earthquakes in stable continental regions11. Historical seismicity, Geophys
 J. Int., Johnston, A.C. & Schweig, E.S
, 1996
"... The sizes of three major or great historical earthquakes are reassessed using the isoseismalarearegression tools developed in Parts I and I1 of this study of stable continental region (SCR) seismicity. The earthquakes are 181 1 New Madrid, central United States, and its following sequence; 1886 Ch ..."
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Cited by 91 (0 self)
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The sizes of three major or great historical earthquakes are reassessed using the isoseismalarearegression tools developed in Parts I and I1 of this study of stable continental region (SCR) seismicity. The earthquakes are 181 1 New Madrid, central United States, and its following sequence; 1886 Charleston, coastal South Carolina; and 1755 Lisbon, oceanic intraplate off the continental shelf of Portugal. The analysis confirms the large size of these events and for the first time places constraints on the uncertainty of their seismic moment release. Because of the exceptionally low seismicwave attenuation of eastern North America (ENA), a separate North American regression of seismic moment on isoseismal area was developed. Additionally, the unknown western extents of the New Madrid isoseismal areas were calibrated with the
Scaling relations for earthquake source parameters and magnitudes
, 1976
"... A data set of 41 moderate and large earthquakes has been used to derive scaling rules for kinematic fault parameters. If effective stress and static stress drop are equal, then fault rise time, z, and fault area, S, are related by z = 16S1/2/(7~3/2~8), where,8 is shear velocity. Fault length (parall ..."
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Cited by 54 (1 self)
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A data set of 41 moderate and large earthquakes has been used to derive scaling rules for kinematic fault parameters. If effective stress and static stress drop are equal, then fault rise time, z, and fault area, S, are related by z = 16S1/2/(7~3/2~8), where,8 is shear velocity. Fault length (parallel to strike) and width (parallel to dip) are empirically related by L = 2W. Scatter for both scaling rules is about a factor of two. These scaling laws combine to give width and rise time in terms of fault length. Length is then used as the sole free parameter ina Haskell type fault model to derive scaling laws relating seismic moment o Ms (20sec surfacewave magnitude), Ms to S and mh (1sec bodywave magnitude) to M s. Observed ata agree well with the predicted scaling relation. The "source spectrum " depends on both azimuth and apparent velocity of the phase or mode, so there is a different "source spectrum " for each mode, rather than a single spectrum for all modes. Furthermore, fault width (i.e., the two dimensionality of faults) must not be neglected. Inclusion of width leads to different average source spectra for surface waves and body waves. These
2004), Importance of small earthquakes for stress transfers and earthquake
"... Abstract. We estimate the relative importance of small and large earthquakes for static stress changes and for earthquake triggering, assuming that earthquakes are triggered by static stress changes and that earthquakes are located on a fractal network of dimension D. This model predicts that both t ..."
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Cited by 44 (8 self)
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Abstract. We estimate the relative importance of small and large earthquakes for static stress changes and for earthquake triggering, assuming that earthquakes are triggered by static stress changes and that earthquakes are located on a fractal network of dimension D. This model predicts that both the number of events triggered by an earthquake of magnitude m and the stress change induced by this earthquake at the location of other earthquakes increase with m as ∼ 10 Dm/2. The stronger the spatial clustering, the larger the influence of small earthquakes on stress changes at the location of a future event as well as earthquake triggering. If earthquake magnitudes follow the GutenbergRichter law with b> D/2, small earthquakes collectively dominate stress transfer and earthquake triggering, because their greater frequency overcomes their smaller individual triggering potential. Using a SouthernCalifornia catalog, we observe that the rate of seismicity triggered by an earthquake of magnitude m increases with m as 10 αm, where α = 1.00 ± 0.05. We also find that the magnitude distribution of triggered earthquakes is independent of the triggering earthquake’s magnitude m. When α ≈ b, small earthquakes are roughly as important to earthquake triggering as larger ones. We evaluate the fractal correlation
Seismological studies at Parkfield VI: Moment release rates and estimates of source parameters for small repeating earthquakes
 Bull. Seismol. Soc. Am
, 1998
"... Abstract Waveform data from a borehole network of broadband seismographic stations have been used to study microearthquakes along the Parkfield segment of the San Andreas fault (SAF). Analysis of almost 10 years of such data demonstrates that much of the seismicity in this region consists of repeati ..."
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Abstract Waveform data from a borehole network of broadband seismographic stations have been used to study microearthquakes along the Parkfield segment of the San Andreas fault (SAF). Analysis of almost 10 years of such data demonstrates that much of the seismicity in this region consists of repeating sequences, quasiperiodic sequences of earthquakes that are essentially identical in terms of waveform, size, and location. Scalar seismic moments have been estimated for 53 of these repeating sequences and combined with equivalent estimates from 8 similar but larger event sequences from the Stone Canyon section of the fault and the main Parkfield sequence. These estimates show that seismic moment is being released as a function of time in a very regular manner. Measurements of the moment release rate, combined with an assumed tectonic loading rate, lead to estimates of the seismic parameters source area, slip, and recurrence interval. Such parameters exhibit a systematic dependence upon source size over a range of 101 ° in seismic moment that can be described by three simple scaling relationships. Several implications of these scaling relationships are explored, including the repeat time of earthquakes, average stress drop, strength of the fault, and heat generated by earthquakes. What emerges from this analysis of moment release rates is a quantitative description of an earthquake process that is controlled by small strong asperities that occupy less than 1 % of the fault area. This means that the fault is highly heterogeneous with respect to stress, strength, and heat generation. Such heterogeneity helps to explain many of the apparent contradictions that are encountered in the study of earthquakes, such as why faults appear weak, why significant heat flow is not observed, how significant high frequencies can be generated by large earthquakes, and how various geologic features such as pseudotachylytes might form.
Semiempirical estimation of strong ground motions during large earthquakes
, 1983
"... A synthesis method is developed for estimating deterministically strong motions during the mainshock, using the records of small events such as foreshocks and aftershocks which occurred within the area of the mainshock fault. This synthesis formulation is based on the kinematic source model of Haske ..."
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Cited by 40 (3 self)
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A synthesis method is developed for estimating deterministically strong motions during the mainshock, using the records of small events such as foreshocks and aftershocks which occurred within the area of the mainshock fault. This synthesis formulation is based on the kinematic source model of Haskell type and the similarity law of earthquakes. The parameters for this synthesis are determined to be consistent with the scaling relations between the moments and the fault parameters such as fault length, width and dislocation rise time. If the ratio of the mainshock moment Mo to the small event one Moe is assumed to be N', then the mainshock fault can be divided into N x N elements, each dimension of which is consistent with that of the small event and N events at each element may be superposed with a specific time delay to correct the difference in the rise time between the mainshock and the small event and to keep a constant slip velocity between them. By means of this method, the mainshock velocity motions are synthesized using the small event records obtained by velocitytypestrongmotionseismographs for 1980 IzuHantoTohoOki Earthquake (M=6.7). The resultant synthesized motions show a good agreement with the observed ones in the frequency range lower than 1 Hz. Further, the synthesis formulation is improved to be applicable to the higher frequency motions, especially acceleration motions. This revised synthesis for the higher frequency motions is effective when we use the records from the small event having the fault length Le=V,•T(Vr: rupture velocity and T: rise time of mainshock). The synthesized accelerograms by this revised method are in good agreement with the observed ones in the frequency range up to 5 Hz. 1.
2002c), Aftershock zone scaling
 Bull. Seismol. Soc. Am
"... Abstract We investigate the distribution of aftershock zones for large earthquakes (scalar seismic moment M 1019.5 N m, moment magnitude, m 7). Mainshocks are selected from the Harvard centroid moment tensor catalog, and aftershocks are selected from the Preliminary Determination of Epicenters (NEIC ..."
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Cited by 36 (14 self)
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Abstract We investigate the distribution of aftershock zones for large earthquakes (scalar seismic moment M 1019.5 N m, moment magnitude, m 7). Mainshocks are selected from the Harvard centroid moment tensor catalog, and aftershocks are selected from the Preliminary Determination of Epicenters (NEIC) catalog. The aftershock epicenter maps are approximated by a twodimensional Gaussian distribution; the major ellipse axis is taken as a quantitative measure of the mainshock focal zone size. The dependence of zone length, l, on earthquake size is studied for three representative focal mechanisms: thrust, normal, and strike slip. Although the numbers of mainshocks available for analysis are limited (maximum a few tens of events in each case), all earthquakes show the same scaling (M l3). No observable scaling break or saturation occurs for the largest earthquakes (M 1021 N m, m 8). Therefore, it seems that earthquake geometrical focal zone parameters are selfsimilar.
Tsunami earthquakes possibly widespread manifestations of frictional conditional stability
 Geophysical Research Letters
, 2002
"... [1] Tsunami earthquakes, shallow events that produce larger tsunamis than expected given their surface wave magnitudes (Ms), typically have long durations and a source spectrum depleted in short period energy. Seven cases of underthrusting tsunami earthquakes provide information on the rupture proce ..."
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Cited by 33 (7 self)
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[1] Tsunami earthquakes, shallow events that produce larger tsunamis than expected given their surface wave magnitudes (Ms), typically have long durations and a source spectrum depleted in short period energy. Seven cases of underthrusting tsunami earthquakes provide information on the rupture processes, but little constraint on geographic distribution or frequency. We compare their rupture characteristics with smaller magnitude earthquakes on circumPacific interplate thrust faults. Comparable moment release time histories are found for large tsunami earthquakes and for many smaller shallow subduction zone earthquakes, with significantly longer durations and additional source complexity than for events deeper than 15 km. Thus, very shallow interplate earthquake ruptures are scale invariant, with variable frictional properties on the plate interface controlling the depth dependent rupture process. Widespread occurrence of small shallow interplate earthquakes with long durations suggests that many subduction faults have frictional properties that may enable large tsunamigenerating earthquakes to occur; fortunately, large shallow
Effects of plate bending and fault strength at subduction zones on plate dynamics
 Journal of Geophysical Research
, 1999
"... Abstract. For subduction to occur, plates must bend and slide past overriding plates along fault zones. Because the lithosphere is strong, significant energy is required for this deformation to occur, energy that could otherwise be spent deforming the mantle. We have developed a finite element repre ..."
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Cited by 32 (2 self)
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Abstract. For subduction to occur, plates must bend and slide past overriding plates along fault zones. Because the lithosphere is strong, significant energy is required for this deformation to occur, energy that could otherwise be spent deforming the mantle. We have developed a finite element representation of a subduction zone in which we parameterize the bending plate and the fault zone using a viscous rheology. By increasing the effective viscosity of either the plate or the fault zone, we can increase the rates of energy dissipation within these regions and thus decrease the velocity of a plate driven by a given slab buoyancy. We have developed a simple physical theory that predicts this slowing by estimating a convecting cell's total energy balance while taking into account the energy required by inelastic deformation of the bending slab and shearing of the fault zone. The energy required to bend the slab is proportional to the slab's viscosity and to the cube of the ratio of its thickness to its radius of curvature. The distribution of dissipation among the mantle, lithosphere, and fault zone causes the speed of a plate to depend on its horizontal length scale. Using the observation that Earth's plate
On the relation between seismic moment and stress drop in the presence of stress and strength heterogeneity
 J. Geophys. Res
, 1979
"... The seismic moment is related by definition to the average slip on the fault plane of an earthquake. Here we derive an exact expression for the seismic moment in terms of a general heterogeneous stress drop distribution and the geometry of the fault of a complex event. We find that the seismic momen ..."
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Cited by 31 (4 self)
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The seismic moment is related by definition to the average slip on the fault plane of an earthquake. Here we derive an exact expression for the seismic moment in terms of a general heterogeneous stress drop distribution and the geometry of the fault of a complex event. We find that the seismic moment is proportional to a weighted integral of the stress drop on the fault. The weight in this linear relationship is the slip for a hypothetical event with the same source geometry but uniform stress drop. This relationship between seismic moment and stress drop depends on geometry. In particular, for multiple sources the weight is reduced by factors of the order of o/R, where 0 is the radius of a typical subfault and R is the radius of the total source area. As a consequence of these results we find that for a given stress drop, a simple fault generates a larger seismic moment han a multiple fault of the same total surface. Conversely, for a given moment and source area, a complex event would need higher stress drops on the subfaults than a simple smooth fault. We test these results with three rectangular models of faulting. The first is a simple, smooth fault with uniform stress drop. The second model is a simple fault with zero stress drop in the central section of the fault. The last model is a complex event where the central section of the fault remains unbroken. We show that the last two models are difficult to distinguish from their farfield radiation.