Storms during nineteen ninety seven ninety eight washed away tons of sand revealing hundreds of stumps the remnants of a sitka spruce forest. It's through a combination of carbon dating the counting of rings. That the date of the last cascade subduction zone quake took place. The earth's surface is made of southern manager plates and many smaller ones. The smaller place creator earthquakes for short duration of fourteen to forty five seconds. That may reach nine point five on the richter scale. They often take place what is called the fault line between these plates. Many people are familiar with the san. Andreas fault march. eleventh twenty. Eleven japan experienced a subduction zone. Quake that lasted more than four minutes. At nine point one. On the richter scale it was the fourth most powerful earthquake in the world since modern record of began in nineteen hundred the shade created a su- nami that reached a hundred and thirty three feet and muga six miles. Inland it move. Japan's main island of honshu eight feet shifted the earth on its axis between four and ten inches. This was an earthquake created by the shifting of the pacific plate finally to help put earthquakes in perspective the loma prieta quake that he will erupted the nineteen eighty nine world series in san francisco. California lasted fifteen seconds. The great san francisco earthquake of nineteen six was eight point six and lasted forty. Five seconds but japan's great earthquake of twenty eleven lasted over four minutes. Nine point one. On the richter scale based on data from oregon seed geographer patrick corcoran. Us gs alaska science center. True mysteries of the pacific northwest will now tour. The predicted minute by minute. Impact of a cascadia subduction zone earthquake on the oregon coast after three hundred twelve years. The cs z can no longer take the strain it ruptures a spot fifty five miles west of cannon beach oregon and quickly spreads alongs the seven hundred miles of its length from british columbia to mendocino california. The north american plate slips fifty seven feet to the south west sliding over the one fuca plate but remember. We're talking about a crushed more than fifty miles deep. The first movement sends a pressure wave that travels through the earth's crust at thirteen thousand miles an hour. It will reach the west coast in ten seconds. The leading edge will hit oregon's cannon beach and seaside thirty seconds later which portland and fifty seconds seattle in another fifty seconds at one point one. It's what seismologist. Call a full rip..