M7.2 - Northern California

Ninety-eight people injured and considerable damage in southwestern Humboldt County. Preliminary estimate of damage in this area from the series of earthquakes is 66 million U.S. dollars. Maximum intensities (VIII) at Ferndale, Honeydew, Petrolia, Rio Dell and Scotia; (VII) at Fortuna and Loleta; (VI) at Eureka. Landslides and rockfalls occurred in the Honeydew-Petrolia area. Liquefaction was noted in areas of the Eel and Mattole River Valleys. Felt throughout much of northern California as far south as San Francisco and southeast to Carson City and Reno, Nevada. Also felt in many areas of southern Oregon. Strong-motion records indicate peak horizontal accelerations of 1.3g at Cape Mendocino and 0.69g at Petrolia. A tsunami was generated with maximum wave heights (peak-to-trough) of 1.1 m. at Crescent City, 0.2 m. at Arena Cove and 0.17 m. at Pt. Reyes, California; 0.2 m. at Port Orford, Oregon; 0.15 m. at Kahului and 0.1 m. at Hilo, Hawaii. Depth 19.2 kilometers from broadband displacement seismograms. FAULT PLANE SOLUTION: P-Waves NP1:Strike=172 Dip=77 Slip=90 NP2:Strike=352 Dip=13 Slip=90 Principal Axes: (T) Plg=58 Azm=82 (P) Plg=32 Azm=262 Comment: The focal mechanism is poorly controlled and corresponds to reverse faulting. The preferred fault plane is NP2. RADIATED ENERGY No. of sta: 10 Focal mech. F Energy 8.3+0.7*10**14 Nm MOMENT TENSOR SOLUTION Dep 6 No. of sta: 17 Moment Tensor; Scale 10**19 Nm Mrr=2.60 Mtt=-0.40 Mff=-2.19 Mrt=1.01 Mrf=-4.11 Mtf=-1.47 Principal axes: (T) Val=5.41 Plg=56 Azm=62 (N) Val=-0.71 Plg=19 Azm=182 (P) Val=-4.70 Plg=28 Azm=282 Best Double Couple:Mo=5.1*10**19 NP1:Strike=51 Dip=25 Slip=142 NP2:Strike=177 Dip=75 Slip=70 CENTROID, MOMENT TENSOR (HRV) Data Used: GDSN L.P.B.: 33S, 97C M.W.: 35S, 66C Centroid Location: Origin Time 18:06:11.8 0.1 Lat 40.25N 0.01 Lon 124.31W 0.01 Dep 15.0 FIX Half-duration 17.6 Moment Tensor; Scale 10**19 Nm Mrr=2.21 0.02 Mtt=-0.79 0.02 Mff=-1.42 0.03 Mrt=0.62 0.07 Mrf=-6.39 0.08 Mtf=0.45 0.02 Principal Axes: (T) Val=7.04 Plg=53 Azm=87 (N) Val=-0.70 Plg=3 Azm=353 (P) Val=-6.34 Plg=37 Azm=261 Best Double Couple:Mo=6.7*10**19 NP1:Strike=331 Dip=9 Slip=68 NP2:Strike=173 Dip=82 Slip=93