document: At least four moderate earthquakes rattled parts of the world , but there was nary a tremor Monday along the New Madrid Fault , where a scientist said a earthquake was likely to occur . `` This is just a normal day , '' said Waverly Person , chief of the U.S. Geological Survey 's National Earthquake Information Center . `` We 're not backing the prediction at all . '' Along the New Madrid Fault , some schools were canceled and residents purchased earthquake emergency kits and others left town , just in case climatologist Iben Browning was right . Browning said there was a 50-50 chance for a major earthquake early this week along the fault , which stretches from Marked Tree , Ark. , northeast through New Marid , Mo. , to Cairo , Ill. . He believes tidal forces can trigger earthquakes , a theory most scientists reject . `` There 's just no way to predict an earthquake precisely , '' said Person , who has been with the U.S. Geological Survey for more than 25 years . `` There are no two earthquakes alike . '' The center received more than 50 calls about the New Madrid forecast Monday morning and hundreds last week , said Person , who began doing interviews for radio and television stations just after midnight . As Person talked , 24 seismographs etched out activity recorded by monitoring equipment in different parts of the United States , ranging from Alaska to Tennessee . A needle jumped a few inches across the seismograph connected to monitoring equipment in Tonopah , Nev. . Person scanned the chart and called to a colleague , `` It may be a nuclear test . That 's where they conduct those tests . '' A few minutes later , the needle jumped again . `` That 's not a test , '' he said . `` That 's a quake . '' With a measured eye , he estimated the quake was magnitude 2.5 to 3.0 on the Richter scale . Quick calculations showed the quake was magnitude 3.5 , centered about 30 miles southwest of Ely , Nev. . Between midnight and evening , four moderate quakes were recorded at Golden . Three were in the South Pacific , a 5.9-magnitude shaker near New Caledonia , and quakes of 5.1 and 5.0 in the area of Tonga . The fourth was a 5.9-magnitude temblor in northern Colombia . A quake of that size can cause considerable damage in a populated area , but are n't considered serious in remote spots . About 800 quakes between magnitudes 5.0 and 5.9 are recorded each year , said USGS spokesman Don Finley in Washington . The Richter scale gauges the amount of energy released by an earthquake . A quake of magnitude 2 is about the smallest felt by humans . An earthquake of 3.5 on the Richter scale can cause slight damage in the local area , 4 moderate damage , 5 considerable damage , 6 severe damage . A 7 reading is a `` major '' earthquake , capable of widespread heavy damage ; 8 is a `` great '' quake , capable of tremendous damage . The big San Francisco Bay area quake last year registered 7.1 on the Richter scale . In 1989 , the earthquake center recorded 14,604 earthquakes , with a magnitude 1 or higher , Person said . An average of 30 a day are recorded . This fall , there have been two in the New Madrid Fault area , magnitude 4.6 on Sept. 26 and magnitude 3.5 on Nov. 9 , which `` is not unusual , '' he said . Although earthquakes can be tracked historically , forecasting them is difficult , if not impossible , Person said . Some people watch precursor activity , but that does n't always lead to an earthquake . Other quakes occur in a swarm over a period of time , he said . Over the years , he has heard countless earthquake predictions . One woman called daily , alerting Person that an earthquake was about to occur , based on the number of birds that crossed her windshield as she drove down the street . The job , he confesses , `` is never boring . ''
extractive_keyphrases: moderate earthquakes earthquake emergency kits richter scale widespread heavy damage countless earthquake predictions earthquake center major earthquake monitoring equipment
abstractive_keyphrases: u.s. geological survey