Prediction of Large Events on a Dynamical Model of a Fault

We present results for long term and intermediate term prediction algorithms applied to a simple mechanical model of a fault. We use long term prediction methods based, for example, on the distribution of repeat times between large events to establish a benchmark for predictability in the model. In comparison, intermediate term prediction techniques, analogous to the pattern recognition algorithms CN and M8 introduced and studied by Keilis-Borok et al., are more effective at predicting coming large events. We consider the implications of several different quality functions Q which can be used to optimize the algorithms with respect to features such as space, time, and magnitude windows, and find that our results are not overly sensitive to variations in these algorithm parameters. We also study the intrinsic uncertainties associated with seismicity catalogs of restricted lengths.Comment: 33 pages, plain.tex with special macros include

Variability in magnitude of paleoearthquakes revealed by trenching and historical records, along the Haiyuan Fault, China

International audiencePaleoseismology provides fundamental data for generalizing earthquake recurrence behavior, by revealing past surface-rupturing events. Determining the size of paleoseismic events is notoriously more challenging than their timing. Paleoearthquakes exposed in trenches are vaguely defined as large enough to break to the surface and often assumed to be similar in size. Here we show an example where the paleoseismic record includes events of both moderate and large magnitudes. At the Salt Lake site on the active left-lateral Haiyuan Fault, northern Tibetan Plateau, a high-resolution stratigraphic sequence recorded three and possibly four events since A.D. 1500, constrained by accelerator mass spectrometry 14 C dating. Historical accounts of earthquake damage in the study region suggest that several earthquakes exposed in the trenches markedly differ in magnitude. With the exception of the most recent M~8 earthquake that occurred in A.D. 1920, two earlier events, which occurred in A.D. 1760 (or 1709) and 1638, respectively, are considerably smaller, with magnitude M < 7 and more likely M~6 or less. Thus, this section of the Haiyuan Fault that broke during moderate-magnitude events failed again after a short interval during a large M w 7.8–8.3 earthquake, as part of a larger multisegment rupture. Our study shows that moderate-magnitude events can be preserved in the stratigraphy and exposed by paleoseismic trenching under ideal conditions, for instance, if sedimentation is fast enough and there is no hiatus in deposition. Eventually, the data presented add to the growing body of paleoseismic records containing events of different magnitudes with a large variability in rupture length and coseismic slip