\begin{tikzpicture}
\draw(0,0) -- ++ (7,0);
\draw[dashed] (0,0)--(0,2);
\draw[dashed] (4,0)--(4,1.5);
\draw[dashed] (7,0)--(7,2);
\draw[latex-latex] (0,2)--(7,2);
\draw(3.5,2)node[above]{$\eta_{a,c}$};
\draw[latex-latex] (0,1.5)--(4,1.5);
\draw(2,1.5)node[below]{$\eta_{a,b}$};
\draw[latex-latex] (4, 1.5)--(7,1.5);
\draw(5.5,1.5)node[below]{$\eta_{b,c}$};
\foreach \x/\y in {0/a, 4/b, 7/c}{
	\draw[circle,fill] (\x,0)circle[radius=1mm]node[below]{$\y$};
}
\draw(0,0) [red, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(2,0) [red, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(4,0) [blue, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(6,0) [blue, very thick] arc[radius=0.5, start angle=180, end angle=0];
\draw(3,0) [black] arc[radius=1, start angle=180, end angle=0];

\draw(9,0) -- ++ (7,0);
\foreach \x/\y in {0/a, 3/b, 7/c}{
	\draw[circle,fill] (\x+9,0)circle[radius=1mm]node[below]{$\y$};
}

\draw(9,0) -- ++ (7,0);
\draw[dashed] (9,0)-- ++(0,2);
\draw[dashed] (12,0)-- ++(0,1.5);
\draw[dashed] (16,0)-- ++(0,2);
\draw[latex-latex] (9,2)-- (16,2);
\draw(12.5,2)node[above]{$\eta_{a,c}$};
\draw[latex-latex] (9,1.5)--(12,1.5);
\draw(10.5,1.5)node[below]{$\eta_{a,b}$};
\draw[latex-latex] (12, 1.5)--(16,1.5);
\draw(14,1.5)node[below]{$\eta_{b,c}$};

\draw( 9,0) [red, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(11,0) [magenta, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(13,0) [blue, very thick] arc[radius=1, start angle=180, end angle=0];
\draw(15,0) [blue, very thick] arc[radius=0.5, start angle=180, end angle=0];
\draw(12,0) [black] arc[radius=1, start angle=180, end angle=0];
\end{tikzpicture}