Frictional fusion due to coseismic landsliding during the 1999 Chi‐Chi (Taiwan) ML 7.3 Earthquake

Fused materials (pseudotachylytes) generated from landsliding during the 1999 Chi‐Chi (Taiwan) ML7.3 earthquake are found on the glide plane in Mio‐Pliocene interbedded shale and siltstone. The pseudotachylytes occur as thin layers on the glide plane and as veins injected into cracks in the host rocks, which are a few mm to 1 cm in thickness. Typical melting textures within the pseudotachylyte include vesicles, glassy matrices, flow structures, and rounded and embayed clast shapes. Powder X‐ray diffraction analysis has revealed a glass content of up to 50 wt% within the pseudotachylyte. Physical conditions of pseudotachylyte formation are estimated to have been <1.5 MPa corresponding to ca.40 m depth, at a temperature of at least 1100∼1600 °C. The geological and petrological data suggests that these pseudotachylytes formed by frictional melting generated from coseismic landsliding during the Chi‐Chi earthquake.

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