<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "> I don't know about 18-wheeler-impact-equivalents, but the Mercalli Intensity scale give a good indication of what you would experience. It's not tied directly to magnitude, however, because it involves mostly the effects on human's and their structures. If an earthquake occurs in a forest...<div><br></div><div>From <a href="http://earthquake.usgs.gov/learning/topics/mercalli.php">http://earthquake.usgs.gov/learning/topics/mercalli.php</a></div><div><br></div><div>The following is an abbreviated description of the 12 levels of Modified Mercalli intensity.<div><br></div><div> I. Not felt except by a very few under especially favorable conditions.</div><div><br></div><div> II. Felt only by a few persons at rest, especially on upper floors of buildings.</div><div><br></div><div> III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.</div><div><br></div><div> IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.</div><div><br></div><div> V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.</div><div><br></div><div> VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.</div><div><br></div><div> VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.</div><div><br></div><div> VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.</div><div><br></div><div> IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.</div><div><br></div><div> X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.</div><div><br></div><div> XI. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.</div><div><br></div><div> XII. Damage total. Lines of sight and level are distorted. Objects thrown into the air.</div><div><br></div><div> <span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div>Craig Messerman</div><div>Sentinel High School, Missoula, MT</div><div>IRIS Seismographs in Schools Station SHMT</div><div>406-728-2400, ext. 7067</div><div><a href="mailto:cmesserman@mcps.k12.mt.us">cmesserman@mcps.k12.mt.us</a></div><div><a href="mailto:cmflyer@bresnan.net">cmflyer@bresnan.net</a></div><div><br class="khtml-block-placeholder"></div><br class="Apple-interchange-newline"></span> </div><br><div><div>On Jan 20, 2009, at 7:14 PM, Carlton Cross wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> <div class="Section1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial","sans-serif"; color:#1F497D"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial","sans-serif"; color:#1F497D"><o:p> </o:p></span></p> <div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Goh83642@wmconnect.com [<a href="mailto:Goh83642@wmconnect.com">mailto:Goh83642@wmconnect.com</a>] <br> <b>Sent:</b> Monday, January 19, 2009 11:00 PM<br> <b>To:</b> <a href="mailto:geysers-bounces@lists.wallawalla.edu">geysers-bounces@lists.wallawalla.edu</a><br> <b>Subject:</b> Earthquake swarm - Question<o:p></o:p></span></p> </div><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Gazers, <br> <br> I have a question about the recent earthquake swarm in the north end of Yellowstone lake. My question isn't so much about the swarm as it is about a relative analogy of how much an earthquake intensity is. In other words, if an earthquake has a magitude of 1.0, how can I compare that to something I can see on a real time example: such as: dropping an 18 wheeler tractor from 100 feet will cause an equivalent of a 1.0 magitude earthquake. <br> Since there were hundreds of earthquakes in magitudes of 1.0 - 3.9 in the swarm, it would sure help to visualize how much shaking it really did to the surface of the earth. <br> If there are any specialists on earthquakes out there, please give this request some thought and let us all know the answer. <br> <br> Regards, Gary Henderson <br> Meridian, Idaho</span><o:p></o:p></p> </div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Geysers mailing list</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="mailto:Geysers@lists.wallawalla.edu">Geysers@lists.wallawalla.edu</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="https://lists.wallawalla.edu/mailman/listinfo/geysers">https://lists.wallawalla.edu/mailman/listinfo/geysers</a></div> </blockquote></div><br></div></body></html>