DOI: 10.5061/dryad.bcc2fqzs1
title: Decadal seafloor geodesy constrains frictionally locked areas along the Nankai Trough

description: Identifying the frictionally locked area of a plate boundary is an
 important geodetic issue in mitigating earthquake disasters, but slow
 slips make it impossible to understand the frictional state via temporally
 averaged geodetic data. This problem is particularly serious at
 sub-seafloor plate boundaries, where long-term geodetic observations are
 difficult. Here, we evaluated long-term slip deficit rate variations in
 the Nankai Trough, the only area in the world for which high-density data
 on horizontal and vertical components have been accumulated via seafloor
 observations with a sufficient frequency on the decadal scale.
 Consequently, we constrained the constantly locked areas and found that it
 was limited mainly to a depth of 10–20 km, with slow slips occurring
 throughout the entire shallow side adjacent to the locked area.
description: # Decadal seafloor geodesy constrains frictionally locked areas along the
 Nankai Trough
 [https://doi.org/10.5061/dryad.bcc2fqzs1](https://doi.org/10.5061/dryad.bcc2fqzs1) --- We have submitted GNSS-A position data (**Data S1: res.$site**), velocity data (**Data S2: $site.data_mvel**), coefficients in SDR inversions (**Data S3: slipcoef_disp_$year_ud**), O-C values in SDR inversions (**Data S4: OC_$year**), and average of standard deviation of coefficients (**Data S5: slipcoef_disp_std_ud**). ## Descriptions ### **Data S1: res.$site** Time series of positions of each observation site in Fig. S1. * *$site*: Site name * *Year*: Observed date * *EW[m]*: Eastward component [m] * *NS[m]*: Northward component [m] * *UD[m]*: Upward component [m] ### **Data S2: $site.data_mvel** Time series of velocities of each observation site in Fig. S1. The time period used to calculate the velocity and its estimation accuracy (velocity ±1σ) are also listed. The eastward, northward, and upward components are listed in order from top to bottom. * *$site*: Site name * *Year*: Center of the range in which the velocity is calculated * *Vel[m/y]*: Calculated velocity [m/y] * *from*: Start of the range for calculating the speed * *to*: End of the range for calculating the speed * *σ-*: Vel-1σ [m/y] (σ: standard deviation in velocity calculation) * *σ+*: Vel+1σ [m/y] ### **Data S3: slipcoef_disp_$year_ud** Coefficients in the “02” (first column) and “03” (second column) directions of each node of Green’s function library when estimating SDR for each period in Fig. 4. * *1st column*: "02" direction of Green’s function library * *2nd column*: "03" direction of Green’s function library ### **Data S4: OC_$year** The observed and calculated values used in the SDR inversion for each epoch in Fig. 5. * *$year*: Time range (ex: "2015" indicates the period from Jan 2013 to Dec 2016) for the SDR inversion * *Lon*: Site longitude * *Lat*: Site longitude * *obs_E(cm/y)*: Eastward component in observed velocity [cm/y] * *obs_N(cm/y)*: Northward component in observed velocity [cm/y] * *obs_U(cm/y)*: Upward component in observed velocity [cm/y] * *cal_E(cm/y)*: Eastward component in calculated velocity [cm/y] * *cal_N(cm/y)*: Northward component in calculated velocity [cm/y] * *cal_U(cm/y)*: Upward component in calculated velocity [cm/y] ### **Data S5: slipcoef_disp_std_ud** The average of standard deviation (Fig. S2) of coefficients in the “02” (first column) and “03” (second column) directions when estimating SDR for the periods. * *1st column*: "02" direction of Green’s function library * *2nd column*: "03" direction of Green’s function library