Evidence for self‐similar, triangular slip distributions on earthquakes: Implications for earthquake and fault mechanics

Abstract

[1] We characterize average slip distributions on earthquakes beyond their individual heterogeneity. For that, we analyze a large number of seismic slip distributions both measured at the surface after earthquakes (44 profiles) and derived from slip inversion models (76 models). Investigating the overall shape of these slip profiles, we find that they are roughly triangular both along strike and dip, and most of them (70-80%) are asymmetric. Long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles. The scaling relations between maximum displacement and length (or width) suggest furthermore that the triangular slip profiles are self-similar. Such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major ''asperity.'' Analyzing the position of hypocenters with respect to these ''asperities,'' we find that earthquakes nucleate at a distance from them that averages 20-30% of their total length. Compiling observations on 56 earthquakes, we show that this distance (i.e., the asperity size) is structurally defined. We then compare the earthquake slip profiles to cumulative slip profiles measured on long-term faults of various ages and sizes and find that all profiles have a similar shape, triangular and asymmetric. Hence combining data for a large number of earthquakes leads to point out average, generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault. This suggests that these characteristics result from robust physical properties.Citation: Manighetti, I., M. Campillo, C. Sammis, P. M. Mai, and G. King (2005), Evidence for self-similar, triangular slip distributions on earthquakes: Implications for earthquake and fault mechanics,

Interpretation and analysis of planetary structures

“…10a) exhibits the characteristics of the displacement (throw) profiles of individual unlinked faults (Barnett et al,1987;see Peacock and Sanderson,1991 for terrestrial examples of displacement profiles of linked faults), i.e., a continuous increase of displacement from the fault tips toward the area of maximum displacement (or throw), which is located at or near the fault's midpoint. The shape of the aggregate displacement profile is in agreement with results from fieldwork and theoretical research, which suggest semi-elliptical or triangular displacement profiles (see Manighetti et al, 2005, and references therein).…”

River profile response to normal fault growth and linkage: an example from the Hellenic forearc of south-central Crete, Greece

“…Displacement profiles often reveal the history of fault growth and linkage for active fault zones ( Fig. 2; Anders and Schlische, 1994;Dawers and Anders, 1995;Gupta and Scholz, 2000;Manighetti et al, 2001Manighetti et al, , 2005Hetzel et al, 2004). When adjacent faults begin to overlap, their stress fields interact, causing their displacement profiles to temporarily deviate from those that are predicted for a singular fault (Fig.…”

Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation

“…10) represent rupture lengths, the potential magnitude of an associated earthquake can be inferred from D-L regressions (Wells and Coppersmith, 1994). However, it is necessary to recall that: (1) part of the surface expression of fault activity may be concealed by sedimentation, especially at tips of overlapping segments, where cumulative displacements are less: this is indeed what is suggested by the along-strike evolution of scar heights, at least for the B and D segments (see H1 evolution, Table 2); (2) surface slip is only a fraction of actual slip at depth, averaging ~ 40% for moderate-size reverse earthquakes (Manighetti et al, 2006); and (3) fault rupture of M > 6 earthquakes often concerns several adjacent fault segments or cracks, inducing large along-strike-slip variability and slip saturation ( [Rubin, 1995] and [Manighetti et al, 2005]). If we hypothesize here that close segments A (~ 30 km), B (~ 30 km), and C (~ 20 km) may break during a single large event, the scaling relations between surface displacement and length (Manighetti et al, 2006) indicate relatively mature fault segments and yield a consistent seismic moment Mo of 1-2 × 1020 Nm and a magnitude Mw of ~ 7.5 (Wells and Coppersmith, 1994), i.e.…”