Comparative Study on Scaling Relations of Source Parameters for Great Earthquakes in Inland Crusts and on Subducting Plate-Boundaries

Abstract

We investigated seismic scaling relations of rupture area S, average slip D, combined area of large-slip area (LSA) SaL, that of strong motion generation area (SMGA) SaS, and acceleration source spectral shortperiod level A versus seismic moment M0 for six crustal earthquakes with 7.5≤Mw≤7.9 in inland crusts and six plate-boundary earthquakes with 8.4≤Mw≤9.1 in subduction zone. We compared our relations obtained above with previous studies, and discussed the difference between source parameters derived from source models based on relatively long-period (10 to 100 s) and short-period (0.1 to 10 s) data. For the crustal earthquakes we confirmed that the scaling relations fit in the relationships suggested by previous studies. On the other hand, for the plate-boundary earthquakes we found a new M0 -S scaling relation of great earthquakes with Mw≳8.4 where S is proportional to M0 1/2 . This corresponds to the second stage in the "three stage scaling model" that is caused by the saturation of fault width due to the restriction of the seismogenic layer in the subduction zone. Moreover we found that SaS of great plate-boundary earthquakes is approximately three times as small as SaL, although M0 -SaL relation fits in the scaling relation, SaL＝0.20･S, suggested by Murotani et al. (2008). These results indicate that source characteristics of great earthquakes on subducting plateboundaries are different from those in inland crusts, especially in the short-period range related to strong ground motions, and that the great plate-boundary earthquakes require some new source models to predict strong ground motions from the scenario earthquakes.

Source‐Scaling Relations of Interface Subduction Earthquakes for Strong Ground Motion and Tsunami Simulation

“…We believe that this might be an indication of fault width saturation. The study of Tajima et al (2013) also suggests saturation at a median width of 200 km, similar to our result in Figure 9. The limited number of data for M > 8:3, and the poor constraint of the fit for M > 9:0, do not provide definitive resolution of width saturation.…”

“…We assumed self-similar scaling laws in performing the regression analysis in the previous section. However, there are studies (e.g., Papazachos et al, 2004;Strasser et al, 2010;Tajima et al, 2013) that suggest a departure from self-similarity of the rupture area and slip of the fault. We relaxed the constraint of self-similarity and fit the data to a non-self-similar relationship of the form E Q -T A R G E T ; t e m p : i n t r a l i n k -; d f 2 ; 3 1 4 ; 4 6 7 logY logc a c b logM 0 ; 2 in which Y corresponds to the different source parameters and c a , c b are the regression coefficients.…”

“…10, solid symbols) justify the linear model up to the maximum magnitude that was used in the regression (M 9.17 for Sumatra 2004 earthquake). However, there are studies (e.g., Blaser et al, 2010;Tajima et al, 2013) Figure 1. Locations of the earthquakes listed in Table 1.…”

“…Source-Scaling Relations of Interface Subduction Earthquakes for Strong Ground Motion and Tsunami Simulation 1655 indicating that beyond a certain magnitude, the fault width tends to a constant value (saturates). We tested this assumption by fitting a bilinear model that saturates for M > 8:4, consistent with the model of Tajima et al (2013). The regression coefficients for the bilinear model are listed in Table 4 as model W 2 and the fit is depicted with the dashed line in Figure 9.…”

Fault model of the 12th century southwestern Hokkaido earthquake estimated from tsunami deposit distributions

“…The depths of the bottom edge of the fault models were fixed based on the estimated seismogenic zone of the crustal structures in the Japan Sea (Sato et al 2014). The slip amount of the fault models was established from scaling relation in relation to seismic moment and area, length, and slip amount of fault models in previous studies (Murotani et al 2010;Tajima et al 2013). Furthermore, a large slip amount area in the shallow part of the fault models was set.…”