I want to arrange a reference axis of «x» values in a figure, as the third axis below in the photo I attached.
I tried to write the code with a third tikzpicture
to resemble an axis scale with values.
\documentclass[12pt,a4paper]{article}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}
\begin{figure}[htb]
\centering
\caption{Registro de sismo de Lima y Callao, 1966}
\begin{tikzpicture}
\begin{axis}[ylabel={\scriptsize $Sa$ (g)}, xmin=0, xmax=70, legend cell align=left,axis lines=middle,xtick=\empty]
\addplot [black] table [col sep=space,x index = 1, y index = 2]{
3270 65.38 -0.000548603
3271 65.4 0.002624689
3272 65.42 0.005662406
3273 65.44 0.004233252
3274 65.46 -0.001235658
3275 65.48 -0.006903344
3276 65.5 -0.006914557
3277 65.52 -0.001607727
3278 65.54 0.002501346
3279 65.56 0.002134373
3280 65.58 -0.001549623
3281 65.6 -0.002156147
3282 65.62 -0.000266239
3283 65.64 0.00042897
};
\addlegendentry{\scriptsize E-O};
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}
\begin{axis}[xlabel={\scriptsize $T$ (s)},
ylabel={
\scriptsize $Sa$ (g)},
xmin=0,
xmax=70,
legend cell align=left,
axis lines=middle,
xtick=\empty]
\addplot [black] table [col sep=space,x index = 1, y index = 2]{
3243 64.84 -0.00198999
3244 64.86 -0.003625056
3245 64.88 -0.001574088
3246 64.9 -0.002725974
3247 64.92 -0.008682141
3248 64.94 -0.014073578
3249 64.96 -0.010333517
3250 64.98 -0.005930866
3251 65 -0.00811843
3252 65.02 -0.006286626
3253 65.04 0.001910112
3254 65.06 0.006209806
3255 65.08 0.002593089
3256 65.1 0.000753129
3257 65.12 0.005030398
3258 65.14 0.008223058
3259 65.16 0.005382079
3260 65.18 0.00023631
3261 65.2 -0.002535352
3262 65.22 -0.002578165
3263 65.24 -0.002353904
3264 65.26 -0.003784077
3265 65.28 -0.004187747
3266 65.3 -0.001268277
3267 65.32 0.001210826
3268 65.34 0.000134373
3269 65.36 -0.001777961
};
\addlegendentry{\scriptsize N-S};
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}
\begin{axis}[xlabel={\scriptsize $T$ (s)},
restrict y to domain=0:0,
xmin=0,
xmax=70,
xtick=\empty]
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}