Fallen utility poles indicative of strong ground movement along Chelungpu Fault during the Chi-Chi (Taiwan) earthquake

We derived strong ground movement from an inclination of utility poles at three localities (Shikung, Tsanton and Mingchien) along the Chelungpu seismic fault during the Chi-Chi (Taiwan) Earthquake: (1) Utility poles on the footwall fell westward, but those on the hanging wall inclined in varied directions. (2) The inclined utility poles near the fault line have larger amounts of opening(s), 5-15 cm wide, against an asphalt layer on a roadway. The ground movement near the fault in the Chi-Chi (Taiwan) Earthquake was bigger than the Kobe Earthquake. (3) The strong ground movement (S greater than or equal to 5 cm) near the fault appeared in a narrow width of less than 100 m on both sides of the fault line, except for Shikung. Damaged housing and buildings are commonly concentrated within the range of the strong ground movement. Therefore, it is significant to clearly know the width of the strong motion strip, for earthquake-resistant design.