152:, such that the stress never builds sufficiently to support rupture propagation. In other cases there is strong evidence for persistent barriers to propagation, giving an upper limit to earthquake magnitude. Rupture length correlates with earthquake magnitude and varies from an order of magnitude of kilometers in the single digits for a magnitude 5–6 earthquake up to hundreds of kilometers for stronger earthquakes (magnitude 7–9), although the correlation is not exact and outliers exist.
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GrimshawC, Hale D, Hall B, Hao KX, Hatem A, Hemphill-Haley M, Heron DW, Howarth J, Juniper Z, Kane T, Kearse J, Khajavi N, Lamarche G, Lawson S, Lukovic B, Madugo C, Manousakis I, McColl S, Noble D, Pedley K, Sauer K, Stahl T, Strong DT, Townsend DB, Toy V, Villeneuve M, Wandres A, Williams J, Woelz S, and R. Zinke (2017).
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in all directions along the fault surface. The propagation will continue as long as there is sufficient stored strain energy to create new rupture surface. Although the rupture starts to propagate in all directions, it often becomes unidirectional, with most of the propagation in a mainly horizontal
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are all associated with strike-slip movement. The rupture cannot accelerate through the
Rayleigh wave limit, so the accepted mechanism is that supershear rupture begins on a separate "daughter" rupture in the zone of high stress at the tip of the propagating main rupture. All observed examples show
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Stirling MW, Litchfield NJ, Villamor P, Van Dissen RJ, Nicol A, Pettinga J, Barnes P, Langridge RM, Little T, Barrell DJA, Mountjoy J, Ries WF, Rowland J, Fenton C, Hamling I, Asher C, Barrier A, Benson A, Bischoff A, Borella , Carne R, Cochran UA, Cockroft M, Cox SC, Duke G, Fenton F, Gasston C,
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Once the rupture has initiated, it begins to propagate along the fault surface. The mechanics of this process are poorly understood, partly because it is difficult to recreate the high sliding velocities in a laboratory. Also the effects of strong ground motion make it very difficult to record
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A tectonic earthquake begins by an initial rupture at a point on the fault surface, a process known as nucleation. The scale of the nucleation zone is uncertain, with some evidence, such as the rupture dimensions of the smallest earthquakes, suggesting that it is smaller than 100 m while other
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evidence, such as a slow component revealed by low-frequency spectra of some earthquakes, suggest that it is larger. The possibility that the nucleation involves some sort of preparation process is supported by the observation that about 40% of earthquakes are preceded by
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Some ruptures simply run out of sufficient stored energy, preventing further propagation. This may either be the result of stress relaxation due to an earlier earthquake on another part of the fault or because the next segment moves by
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are dangerous because most of the energy release happens at lower frequencies than normal earthquakes and they lack the peaks of seismic wave activity that would alert coastal populations to a possible tsunami risk. Typically the
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Rosakis, A.J.; Xia, K.; Lykotrafitis, G.; Kanamori, H. (2009). "Dynamic Shear
Rupture in Frictional Interfaces: Speed, Directionality and Modes". In Kanamori H. & Schubert G. (ed.).
171:, 0.92 of the shear wave velocity, typically about 3.5 km per second. Observations from some earthquakes indicate that ruptures can propagate at speeds between the S-wave and
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Figure 1. This cartoon shows what happens at the surface due to an earthquake rupture. Notice the progression of the strain that leads to the fault and amount of displacement.
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direction. Depending on the depth of the hypocentre, the size of the earthquake and whether the fault extends that far, the rupture may reach the ground surface, forming a
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Slower than normal rupture propagation is associated with the presence of relatively mechanically weak material in the fault zone. This is particularly the case for some
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Propagation may take place on a single fault, but in many cases the rupture starts on one fault before jumping to another, sometimes repeatedly. The
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evidence of a transition to supershear at the point where the rupture jumps from one fault segment to another.
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velocity, with only a minority of ruptures propagating significantly faster or slower than that.
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was particularly complex, with surface rupture observed on at least 21 separate faults.
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Extremely slow ruptures take place on a time scale of hours to weeks, giving rise to
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National
Research Council (U.S.). Committee on the Science of Earthquakes (2003).
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went almost unnoticed, but the associated tsunami killed more than 22,000 people.
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or are simply a result of increasing stresses in the region of the mainshock.
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58:. Earthquakes occur for many reasons that include: landslides, movement of
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353:"Time distribution of immediate foreshocks obtained by a stacking method"
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as the former does not capture the longer wavelength energy release. The
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Seismicity patterns, their statistical significance and physical meaning
447:. Menlo Park, California: DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY
359:. Reprint from Pageoph Topical Volumes. Birkhäuser. pp. 381–394.
83:., have no foreshocks and it remains unclear whether they just cause
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Extent of slip in the Earth's crust that occurs during an earthquake
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for most of its propagation before finally jumping again onto the
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Most ruptures propagate at speeds in the range of 0.5–0.7 of the
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Bulletin of the New
Zealand Society for Earthquake Engineering
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Living on an Active Earth: Perspectives on
Earthquake Science
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Microearthquake seismology and seismotectonics of South Asia
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Following nucleation, the rupture propagates away from the
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The upper limit to normal propagation is the velocity of
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127:, the Sutsina Glacier Thrust, before jumping onto the
285:. Washington D.C.: National Academies Press. p.
258:(New York: W. W. Norton & Company, 2001): 305–6.
112:, below which the deformation starts to become more
79:. However, some large earthquakes, such as the M8.6
277:"5. Earthquake Physics and Fault-System Science"
355:. In Wyss M., Shimazaki K. & Ito A. (ed.).
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425:: CS1 maint: multiple names: authors list (
511:(2 ed.). Springer. pp. 129–138.
91:information close to a nucleation zone.
470:. Treatise on Geophysics. Vol. 4.
440:Mark, R.K.; Bonilla, Manuel G. (1977).
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196:for such an event is much smaller than
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62:in a volcano, the formation of a new
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480:10.1016/B978-0-444-53802-4.00072-5
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505:"5. Earthquake-generated tsunami"
541:"Slow Earthquakes: An Overview"
509:Tsunami: the underrated hazard
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394:7.8 2016 KaikĹŤura earthquake"
226:Earthquake duration magnitude
81:1950 India - China earthquake
256:Earth: Portrait of a Planet
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413:10.5459/bnzsee.50.2.73-84
323:. Springer. p. 15.
137:2016 KaikĹŤura earthquake
202:1896 Sanriku earthquake
194:surface wave magnitude
185:megathrust earthquakes
177:supershear earthquakes
121:2002 Denali earthquake
50:that occurs during an
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468:Earthquake Seismology
135:. The rupture of the
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317:Kayal, J.R. (2008).
231:Earthquake magnitude
503:Bryant, E. (2008).
236:Epicentral distance
189:tsunami earthquakes
474:. pp. 11–20.
351:Maeda, K. (1999).
44:earthquake rupture
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143:Termination
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162:shear wave
101:hypocentre
77:foreshocks
70:Nucleation
52:earthquake
40:seismology
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472:Elsevier
215:See also
156:Velocity
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