On the basis of the pulse width broadening of initial P waves, temporal change of QP-1 was investigated for the focal area of the 1984 western Nagano, central Japan earthquake of M=6.8. QP-1 in the focal area, ranging between 3.9¿10-3 and 10.0¿10-3, was significantly higher than that of the surrounding area, 2.8¿10-3, throughout the 1.3-year postseismic stage that we examined. The highest value, however, appeared not just after the main shock but for the period from 1 day to 2 months following the main shock. After the maximum attenuation was attained, QP-1 in the focal area monotonically decreased, approaching the value of the surrounding area. This characteristic feature of QP-1 change is successfully accounted for by the model in which newly opened cracks are gradually saturated by interstitial fluid. QP-1 of the focal area was much higher than the surrounding area even for the period prior to the main shock. The high attenuation of the preseismic stage is probably a consequence of the earthquake swarm which preceded the M=6.8 earthquake. However, there remains a possibility that attenuation intensity in the focal area increased as a precursor to the western Nagano earthquake. ¿American Geophysical Union 1987