![]() Why can't scientists agree on magnitudes for earthquakes?įor older earthquakes, the data are often of poor quality or the few stations existing at the time may not have been in the best locations to record the information needed. Each unit step in moment magnitude is equivalent to roughly a factor of 32 in energy release, thus it would require rougMw=6.9 Loma Prieta earthquakes occurring simultaneously to equal the energy release of 1906. This magnitude is directly proportional to energy release and can be obtained from analysis of broad-spectrum seismograms or from the product of the rupture area and average fault slip. Richter arbitrarily chose a magnitude 0 event to be an earthquake that would show a maximum combined horizontal displacement of 1m (0.00004in) on a seismogram recorded using a Wood-Anderson torsion seismograph 100km (unknown operator: u'strong'mi) from the earthquake epicenter. The preferred descriptor for large earthquakes rich in low frequencies is the moment magnitude as used by Thatcher et al (above). However, the Richter magnitude scale was developed for local earthquakes recorded on high-frequency seismometers. The traditional magnitude of 8 1/4 or 8.3 comes from Richter (1958). Based on the amount of slip, these models suggest a moment-magnitude (Mw) of 7.9. Using the observed changes, these scientists constructed models of the slip distribution on the fault plane in 1906. This deformation manifests itself as changes in the angles and distances between benchmarks in geodetic networks. The offset on the fault plane produces ground deformation over a broad region around the fault. Wayne Thatcher, Grant Marshall, and Michael Lisowski (USGS) have re-evaluated the geodetic data from before and after the 1906 earthquake. They also found that most of the shaking energy came from two separate areas on the fault - one between Point Reyes and Fort Ross to the north and the second on the San Francisco Peninsula to the south. Data from 12 of these observatories were of good enough quality to be digitized and modeled, and suggest a surface wave magnitude (Ms) of 7.7. This article has been rated as High-importance on the project's importance scale.The magnitude of 1906 has been redetermined in two recent studies that used rather different approaches: M = 7.7ĭavid Wald, Hiroo Kanamori, Donald Helmberger, and Thomas Heaton (Cal Tech and USGS) studied recordings of the 1906 seismic waves made at 96 observatories around the world. New Zealand Wikipedia:WikiProject New Zealand Template:WikiProject New Zealand New Zealand articles If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks. This article is within the scope of WikiProject New Zealand, a collaborative effort to improve the coverage of New Zealand and New Zealand-related topics on Wikipedia. This article has been rated as Mid-importance on the project's importance scale. This article has been rated as B-class on Wikipedia's content assessment scale. Earthquakes Wikipedia:WikiProject Earthquakes Template:WikiProject Earthquakes WikiProject Earthquakes articles If you would like to participate, you can choose to edit the article attached to this page (see Wikipedia:Contributing FAQ for more information), or join by visiting the project page. This article is part of WikiProject Earthquakes, a project to systematically present information on earthquakes, seismology, plate tectonics, and related subjects. This article is of interest to the following WikiProjects: According to the relevant style guide, this should not be changed without broad consensus.Ī news item involving 2010 Canterbury earthquake was featured on Wikipedia's Main Page in the In the news section on 4 September 2010.Ī fact from this article was featured on Wikipedia's Main Page in the On this day section on September 4, 2011, September 4, 2013, September 4, 2016, September 4, 2019, and September 4, 2021. This article is written in New Zealand English, which has its own spelling conventions ( colour, realise, analyse, centre, fiord) and some terms that are used in it may be different or absent from Australian, British, and other varieties of English. ![]()
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