OpenHazards.com - Earthquake Forecasting
https://openhazards.com/faq/earthquake-forecasting
enIs the seismic gap theory valid and reliable?
https://openhazards.com/faq/earthquake-forecasting-user-submitted-questions/seismic-gap-theory-valid-and-reliable
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>The seismic gap theory says that, if there have been large earthquakes on an active fault's neighboring faults in the past, will that unbroken piece of fault be the most likely location for the next major earthquake? A considerable amount of research has tried to answer this question, and at the present time the answer seems to be "no." One reason might be that the unbroken piece of fault is just stronger than the surrounding faults, and it takes much more tectonic stress to break it. Or it may be that the tectonic forces on the unbroken fault have actually been reduced by the earthquakes on the neighbors (this may happen for various reasons arising from the physics of the way stress is transferred through the ground).</p>
<p>In either case, it is possible the unbroken "gap" will persist for some time before it eventually does rupture. This is what makes earthquake forecasting and prediction so difficult.</p>
<p>A frequently cited example of a seismic gap being filled was the magnitude 7 Loma Prieta earthquake of October 17, 1989. An example of an expected great earthquake failing to happen is the Tokai earthquake southwest of Tokyo. This magnitude 8+ event has been anticipated for several decades, but has yet to occur.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div><div class="field-item odd"><a href="/faq/user-submitted-questions" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">User Submitted Questions</a></div></div></div>Sat, 23 Feb 2013 02:34:46 +0000pbrundle595 at https://openhazards.comhttps://openhazards.com/faq/earthquake-forecasting-user-submitted-questions/seismic-gap-theory-valid-and-reliable#commentsIs there any way to predict where the next big earthquake is likely to occur?
https://openhazards.com/faq/earthquake-forecasting-user-submitted-questions/there-any-way-predict-where-next-big-earthquake
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>Right now, an accurate prediction of the location of the next major earthquake is not possible. However, regions of high probability for the next large earthquake can be identified and mapped. In fact, the <a href="/forecast">Personal Earthquake Forecast tool</a> (under the Tools tab) here on this web site can display the probability that a major earthquake will occur within 50 miles of any location you choose.</p>
<p>If you're really curious, we also offer a more powerful tool called the <a href="/viewer">Earthquake Viewer</a> that you can use to find earthquake probabilities in regions of any size. John has written blogs (<a href="/blogs/john/how-make-your-own-earthquake-forecast-anywhere-earth-earthquake-forecast">here</a> and <a href="/blogs/john/make-simple-1-click-forecast-earthquake-forecast">here</a>) explaining how to use the Earthquake Viewer. On that tool, you can click on the bar that says "Select Forecast", and you will see a color contour map of major earthquake probabilities for any location on earth.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div><div class="field-item odd"><a href="/faq/user-submitted-questions" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">User Submitted Questions</a></div></div></div>Sat, 23 Feb 2013 01:30:50 +0000pbrundle594 at https://openhazards.comhttps://openhazards.com/faq/earthquake-forecasting-user-submitted-questions/there-any-way-predict-where-next-big-earthquake#commentsWhat magnitude earthquakes can OpenHazards forecast?
https://openhazards.com/faq/earthquake-forecasting/what-magnitude-earthquakes-can-openhazards-forecast
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>The Open Hazards method generally computes probabilities for the
occurrence of earthquakes in space and time, and for magnitudes
typically larger than M > 5.0. In addition, the methods can be more
specifically applied to compute probabilities for other magnitude
ranges. For example Open Hazards methods have been applied to compute
the probabilities for great earthquakes having magnitudes M > 8.0 in
regions such as Indonesia where these occur.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:58:22 +0000jrholliday36 at https://openhazards.comHow does OpenHazards validate its forecasts?
https://openhazards.com/faq/earthquake-forecasting/how-does-openhazards-validate-its-forecasts
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>Open Hazards validates its forecasts using the same types of
statistical testing that are used in the weather/climate/financial
forecasting communities. These tests are used to determine <em>resolution</em>, the ability of a forecast to discriminate between alternative outcomes; <em>reliability,</em> whether the predicted frequency of events matches the observed frequency of events; and <em>sharpness</em>,
whether events tend to occur at high forecast probabilities, and no
events tend to occur at low forecast probabilities, in contrast to
methods in which events tend to occur near average values of
probability.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:56:56 +0000jrholliday35 at https://openhazards.comHow are probability forecasts typically validated?
https://openhazards.com/faq/earthquake-forecasting/how-are-probability-forecasts-typically-validated
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>Forecasts are validated by a process called <em>backtesting</em> as well as a process called <em>monitoring</em>.
In backtesting, data from the past are divided into a training period
(prior data) and a testing period (posterior data). Forecasts are made
using prior data to forecast events that occur during the posterior
interval. The accuracy of these forecasts are then scored by a variety
of statistical tests. Forecasts that achieve a pre-determined level of
accuracy are considered to be validated at the observed <em>confidence level</em>.
In monitoring, actual real time forecasts are computed, then actual
events are observed. The results are scored using the same types of
statistical analysis. Many researchers consider monitoring to be a
higher level of validation than backtesting, since the “answer” is not
known in advance. However, monitoring can take many years to determine
the accuracy of a forecast method, whereas backtesting typically leads
to an answer within days, weeks, or a few months at most.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:56:12 +0000jrholliday34 at https://openhazards.comWhat methods are currently used for earthquake forecasting?
https://openhazards.com/faq/earthquake-forecasting/what-methods-are-currently-used-earthquake-forecasting
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p class="MsoNormal">The United States Geological Survey, through its
Working Groups on California Earthquake Probabilities, has been
developing long term earthquake forecasts for regions in California
since 1988. These forecasts are based on data describing historic
averages of major earthquakes as well as <em>paleoseismic</em>
geologic data, obtained from trenching studies on active fault traces,
and instrumental data. The result of these studies are 30 year
probabilities for major earthquakes, typically having magnitudes M >
6.7, on major earthquake faults in California. The process by which
these probabilities are computed is an extensive consultation and
collaboration among over 100 scientists lasting several years. Expert
opinion plays a significant role as well. An analysis of these
forecasts was recently published in the scientific journal Nature
("Shaking Up Earthquake Theory, Nature, volume 46, pp. 870-872, 15
October, 2009). </p>
<p class="MsoNormal">Other forecasts include the Accelerated Moment
Release (AMR) method, pioneered by scientists in the United States and
Europe; the Epidemic Type Aftershock Sequence (ETAS) method developed
by scientists in Japan, the United States and Europe; M8 and the
Reverse Tracing of Precursors (RTP) method developed by scientists in
Russia; the Psi method developed by scientists in New Zealand; the USGS
STEP method for computing 24 hour probabilities of ground shaking due
to aftershocks of major earthquakes; and a variety of methods based on
earth strain and ground deformation measures. </p>
<p class="MsoNormal"> The OH forecasts use methods that are based on
ideas that have been in the peer reviewed literature for the past
decade or more. These methods are data driven, using the ANSS catalog
of earthquakes from online sources, together with well known
observational laws including the Gutenberg-Richter relation and the
Omori-Utsu aftershock frequency law. When the parameters in these laws
are fit to the past observations, future probabilities can be computed.
An example of a method of this type is the USGS STEP method, which is
used to compute 24 hour aftershock probabilities. The advantage of the
OH method is that it can be applied in a uniform way world-wide, and
does not require local knowledge of the geology. Methods similar to
this have been repeatedly tested over the past years, and continue to
be tested by a variety of statistical techniques. The resulting
forecasts may differ from the official forecasts as developed by the US
Geological Survey, which uses the method as described above. </p>
<p class="MsoNormal">OH forecasts are fully time- and space-dependent,
so calculated earthquake risk will change both as a result of changing
earthquake probabilities, as well as changing human exposure. Even
without the occurrence of a large earthquake and its aftershocks,
earthquake probabilities can increase or decrease by as much as several
per cent per month in active areas.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:55:21 +0000jrholliday33 at https://openhazards.comAre earthquake forecasts currently being made?
https://openhazards.com/faq/earthquake-forecasting/are-earthquake-forecasts-currently-being-made
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>Yes. The official forecast for the state of California is a
collaboration between the US Geological Survey, the California
Geological Survey, and a large group of scientists from universities
and commercial companies. These forecasts are used to set earthquake
insurance rates in California.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:54:35 +0000jrholliday32 at https://openhazards.comWhat is probabilistic forecasting?
https://openhazards.com/faq/earthquake-forecasting/what-probabilistic-forecasting
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>Probabilistic forecasting involves the computation of a spatial
probability density function together with a temporal probability,
leading to a conditional probability. The latter is the probability
that an earthquake of a specified magnitude will occur, conditioned on
the observation that no earthquake has occurred in the recent past. An
example of a forecast probability statement might be that "there is a
40% probability that an earthquake having a magnitude between 6.5 and
7.0 will occur within a 20 km radius around location X during the next
3 months."</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:53:53 +0000jrholliday31 at https://openhazards.comWhat is forecasting (in contrast to prediction)?
https://openhazards.com/faq/earthquake-forecasting/what-forecasting-contrast-prediction
<div class="field field-name-field-detailed-question field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even" property="content:encoded"><p>While the dictionary defines forecasting to be a synonym for
prediction, we consider forecasting to be a specification of the odds,
or probability, of an earthquake occurring at a given location, during
a given time window, within a given magnitude range. By contrast, we
consider a prediction to be the specification that an earthquake either
will, or will not, occur at a given location, during a given time
window, within a given magnitude range. A forecast is therefore a
statement of probability, whereas a prediction is a binary statement.
An individual forecast can never be validated by a single observation,
but a forecast method can be validated by many observations. By
contrast, an individual prediction can be validated by a single
observation.</p></div></div></div><div class="field field-name-taxonomyextra field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/faq/earthquake-forecasting" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Earthquake Forecasting</a></div></div></div>Thu, 11 Feb 2010 05:53:16 +0000jrholliday30 at https://openhazards.com