Long aftershock sequences within continents and implications for earthquake hazard assessment

Abstract

One of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries. Plate tectonics gives no insight, however, into where and when earthquakes will occur within plates, because the interiors of ideal plates should not deform. As a result, within plate interiors, assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes. Here, however, we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago. We present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded. Aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries. These predictions are in accord with observations. So the common practice of treating continental earthquakes as steady-state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere.

Statistical estimation of the duration of aftershock sequences

“…Here we will show that this inconsistent model assumption can also lead to biased results in ETAS estimation and that applications of the ETAS model with temporally limited aftershock triggering leads to p-value estimates that are more consistent with the rate-and-state friction model. While some previous analysis was performed rather qualitatively, for example (Stein & Liu 2009), we estimate for the first time the duration of the triggering process by means of the modified ETAS model fitted to observed catalogue data. In particular, we want to distinguish between three different timescales of an aftershock process:…”

Thermal weakening localizes intraplate deformation along the southern Australian continental margin

“…Plate tectonics readily accounts for deformation of plate boundaries but does not 28 satisfactorily explain deformation and seismicity of plate interiors (Stein and Liu, 2009 terrace >1000 km long that was exposed ~15 Myr ago by long-wavelength uplift of the SAM 99 (Sandiford, 2007 where E S is the radiated seismic energy (Joules) and M S is the measured surface wave 172 magnitude (Scholz, 2002). 173 that much of Australia's ongoing seismicity might be episodic rather than temporally and 216 spatially stationary, as advocated by Leonard (2008).…”

Experimental Investigation of Visuali Zation Methods of Earth Quake Catalogue Maps

“…Locations of past small earthquakes are good predictors of the location of future ones (Kafka 2007), so the earthquake catalogues are very important for this purpose. In contrast, according to some scientists (Stein, Liu 2009), these small earthquakes may be the aftershocks of past large ones; therefore, these shocks cannot be automatically considered good indicators of future large earthquakes (Stein et al 2012). Hungary is at moderate risk of earthquakes, where earthquakes measuring M4-5 on the Richter scale occur every 15-20 years, while those measuring M6.0 or more occur only every 100-150 years.…”