 The CSMIP Cape Mendocino station was installed in 1978 and was located just 4 kilometers ( 2 @.@ 5 mi ) from the epicenter on the slope of a ridge in the coast ranges . The instruments there had been mounted on a concrete platform adjacent to a roadway and remained firmly secured to the rock platform following the shocks . A landslide came within 50 meters ( 160 ft ) of the device and left debris on the road , but a lack of large rocks close to the instrument and no cracking of the rocks near the platform left geologists with no clear explanation for the extraordinarily high vertical component reading of 1.85g. The tri @-@ axial analog accelerometer that was in use was physically limited to that value and all three traces had uniformly significant values at three seconds into the recording . A post @-@ earthquake lab test of the seismometer and an inspection of the photographically enlarged accelerogram revealed that the limit was hit twice , with a maximum deflection of 31 mm , as the needle bounced off the unit 's mass . An extrapolation of the vertical record led to a maximum acceleration estimate of 2.2g for that site , and the unit was eventually replaced with a higher capacity digital device . 
