SCEC Award Number 12206 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title EARTHQUAKE MAGNITUDE LIMITS
Investigator(s)
Name Organization
Yan Kagan University of California, Los Angeles David Jackson University of California, Los Angeles
Other Participants
SCEC Priorities 2b, 4e, 2e SCEC Groups Seismology, CSEP, EFP
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 The upper limit to earthquake size in any given region is important for designing critical facilities, for comparing earthquake and tectonic moment rates, and for understanding the relationship of earthquakes to stress, material properties, fault and plate geometry, and many other features which might affect earthquake rupture. Unfortunately, it is one of the hardest quantities to determine because large quakes are very rare and one never knows whether the GCMT (Ekstrom et al., 2012) catalog contains an earthquake near the limit. Our objective is to make reasonable, testable estimates of parameters that reflect the limits of earthquake size. Our ultimate objective is to construct a model for computing and testing the probability that an earthquake of any large size will occur within a specified region and time. We'll make the model by estimating the three parameters of a tapered Gutenberg-Richter (TGR) distribution. Testing will be done by comparing the hypocenters of very large earthquakes with our computed probabilities using the CSEP methods (Kagan & Jackson, 1995; Schorlemmer & Gerstenberger, 2007; Schorlemmer et al., 2010).
Intellectual Merit Our ultimate objective is to construct a model for computing
and testing the probability that an earthquake of any large
size will occur within a specified region and time.
In this work we determined the maximum (corner) magnitude for
18 major subduction zones, where the most intensive shallow
earthquakes are supposed to occur.
Broader Impacts Our work on earthquake forecasting and its testing has been extensively reported in scientific literature (see below the list of publications) as well as in many presentations at meetings and workshops. The 11 March 2011 Tohoku, Japan, magnitude 9.1 earthquake and the ensuing tsunami near the east coast of the island of Honshu caused nearly 20,000 deaths and more than 300 billion dollars in damage, resulting in the worst natural disaster ever recorded (Geller, 2011; Stein et al., 2011). The major issue in the enormous damage was a great difference between the expected and the observed earthquake magnitudes. The maximum magnitude size for Tohoku area (around 7.7) was proposed in the official hazard map (Geller, 2011; Stein et al., 2011; Simons et al., 2011; Kagan et al., 2012). The evaluation of maximum possible earthquake was discussed in several of our previous publications. We prepared a few manuscripts (now in review) which update and enhance our results, we again propose that magnitude 9.0-9.7 earthquake are to be expected in subduction zones. These new results were reported in a several scientific meetings.
Exemplary Figure Fig. 3. The corner moment magnitude m_c distribution in the Flinn-Engdahl subduction zones. GCMT catalog 1977-1995/6/30 and 1977--2011 is used. The region's m_c (blue stars) and +/-1.96 standard deviations (cyan polygon) are shown, the black solid line corresponds to the average = 9.36 for all subduction zones, black dashed lines show +/- 0.27 times 1.96 , i.e., 95% confidence limits for the average corner magnitude estimate. In m_c calculations we use the parameters of the tectonic motion as proposed by Bird & Kagan (2004): width of seismogenic zone W = 104 km, shear modulus mu = 49 GPa, chi = 0.5. Green circles show earthquakes with the maximum magnitude m_o which occurred in the regions during the 1977-1995/6/30 catalog time interval. The green line corresponds to the average = 7.69 for all subduction zones for the same time. Magenta `x's and the line show the maximum magnitude m_o data for the time interval 1977--2011, the average is = 8.02. Red squares indicate magnitudes of giant earthquakes during 1995/6/30--2011.
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