Coseismic and early postseismic slips associated with the 2011 off the Pacific coast of Tohoku Earthquake sequence: EOF analysis of GPS kinematic time series

Abstract

GPS kinematic time series are analyzed to estimate slip distributions for the M w 9.0 2011 off the Pacific coast of Tohoku Earthquake sequence. Empirical orthogonal function (EOF) analysis is employed to enhance the signal-to-noise ratio of the original time series. The coseismic, and subsequent postseismic, deformations of the foreshock can be described by a single mode, suggesting that the extent of the source for both events must be similar. The total moment magnitude of the afterslip following the foreshock is estimated to be M w 7.1 with a decay time of 0.63 days. The magnitude of the afterslip was larger for its duration than was anticipated by the scaling law for a typical slow earthquake, although two previous earthquakes in adjacent regions showed the same tendency as that in the present case. The pattern of slip of the mainshock and the subsequent afterslips and aftershocks indicates that each slip occurs in a region adjacent to that of the previous slips in a complementary manner. Finally, in the course of the EOF analysis, the modes representing the thermal expansion of the GPS pillars are clearly identified.

Post-seismic slip of the 2011 Tohoku-Oki earthquake from GPS observations: implications for depth-dependent properties of subduction megathrusts

“…The estimated scalar moment M 0 and moment magnitude M w associated with our solution are respectively, 3.02 × 10 22 Nm and 8.96, assuming a rigidity of 40 GPa. Such a rupture distribution, that predominantly extends in the shallowest part of the fault and reaches the trench with high slip values, appears different from the models estimated from GPS onshore data only (Miyazaki et al 2011;Ozawa et al 2011;Evans & Meade 2012;Munekane 2012) and agrees with the solutions from other studies that used ocean bottom pressure-gauges, different kinds of seismic and strong motions data and GPS/acoustic technique data to estimate the coseismic slip (Ide et al 2011;Shao et al 2011;Iinuma et al 2012;Ozawa et al 2012;Romano et al 2012). On the basis of the previously described resolution test, we can see that the estimated coseismic rupture lies in an area in which the high resolution allows to give confidence to spatial features of the coseismic slip down to a wavelength of about 60 km.…”

“…14). Furthermore the model of early post-seismic slip by Munekane (2012) shows that soon after the main shock and before the two M w > 7 aftershocks, the afterslip does not extend south of 37…”

“…All models show thrust faulting mechanism with the maximum amount of slip varying from about 25 m (Ozawa et al 2011;Munekane 2012) to about 60 m Evans & Meade 2012;Ozawa et al 2012) up to about 80 m Iinuma et al 2012). The studies that used only onshore data (Miyazaki et al 2011;Ozawa et al 2011;Evans & Meade 2012;Munekane 2012) are characterized by a compact slip area which is localized around the earthquake epicentre whereas a significant amount of slip near the trench has been inferred from inversions that involved different kinds of seismic and strong motions data, ocean bottom pressuregauges and GPS/acoustic technique data (Ide et al 2011; Shao et al (Sella et al 2002;Apel et al 2006). The stars represent the USGS (green), JMA (yellow) main shock epicentres and centroid location from GCMT (white).…”

Stress‐driven relaxation of heterogeneous upper mantle and time‐dependent afterslip following the 2011 Tohoku earthquake

“…The LAM fits well the overall curvature of the time series of the GEONET and GPS‐A stations. A constant underestimate of a few centimeters in the east component of 950172 and 940049 (top image in Figure a) may be due to 3‐D structural heterogeneities (see discussion in section 5.1) or very rapid afterslip in the hours to a few days following the event [e.g., Munekane , ], which is not considered in this work. It is the fit to the curvature of the time series that determines how well the Burgers rheology represents the rapidly decaying postseismic deformation.…”

Seismic attenuation tomography of the Northeast Japan arc: Insight into the 2011 Tohoku earthquake (Mw9.0) and subduction dynamics

“…Comparison of Qp and Qs tomography in the megathrust zone (the same as Figure ) with the coseismic slip of the large foreshock ( M w 7.3) (black contours with interval of 0.5 m) [ Ohta et al ., ], the coseismic slip of the main shock ( M w 9.0) (blue contours with interval of 10 m) [ Iinuma et al ., ], the coseismic slips of two large aftershocks ( M w 7.4 and M w 7.7) (pink contours with interval of 0.2 m and 1.26 m, respectively) [ Munekane , ; Kubo et al ., ], and the afterslip from 2 March to12 October 2011 (red contours with interval of 1 m) [ Ozawa et al ., ]. The other labeling is the same as that in Figure .…”