The regional mapping of the 3.SkHz echo characters in the areas off northeastern Taiwan provided valuable information about sedimentary processes on the sea floor. Seven distinctive echo types were recognized. These echo types were grouped into four major classes: indistinct, distinct, hyperbolic and irregular echoes. Indistinct echoes had three sub-classes: prolonged, prolonged with irregular saw-toothed surface and prolonged or semiprolonged with inclined sub-bottom reflectors cropping out laterally. Besides, the hyperbolic class included the large irregular hyperbolae and the broad gently rolling hyperbolae. The irregular echoes were similar to the distinct type but with a jumbled morphology.
The echo character map showed that each of the physiographic provinces was characterized by a distinctive echo type. The very prolonged echo occurring on the narrow llan continental shelf indicated that strong current activities prevailed in this region. The upper part of the continental slope, characterized by large irregular hyperbola, was dominanted by slumping and/or sliding processes. Meanwhile, the turbidity currents and mass-wasting processes had apparently been the primary agents shaping the lower part of the slope as indicated by the distinct echoes.