View source for Earth:Intraplate earthquake

{{short description|Earthquake that occurs within the interior of a tectonic plate}}
{{Earthquakes}}
[[File:New Madrid Seismic Zone activity 1974-2011.svg|thumb|Distribution of seismicity associated with the [[Earth:New Madrid Seismic Zone|New Madrid Seismic Zone]] (since 1974). This zone of intense earthquake activity is located deep within the interior of the North American plate.]]
The term '''intraplate earthquake''' refers to an [[Earth:Earthquake|earthquake]] that occurs ''within the interior'' of a [[Earth:Plate tectonics|tectonic plate]]; this stands in contrast to an [[Earth:Interplate earthquake|interplate earthquake]], which occurs ''at the boundary'' of a tectonic plate. Intraplate earthquakes are often called "intraslab earthquakes," especially when occurring in microplates.<ref>{{Cite journal|last1=Iwata |first1=Tomotaka |last2=Asano |first2=Kimiyuki |year=2011 |title=Characterization of the Heterogeneous Source Model of Intraslab Earthquakes Toward Strong Ground Motion Prediction |journal=Pure and Applied Geophysics |volume=168 |issue=1–2 |pages=117–124 |doi=10.1007/s00024-010-0128-7 |s2cid=140602323 }}</ref><ref>{{Cite journal|last1=Senoa |first1=Tetsuzo |last2=Yoshida |first2=Masaki |year=2004 |title=Where and why do large shallow intraslab earthquakes occur? |journal=Physics of the Earth and Planetary Interiors |volume=141 |issue=3 |pages=183–206 |doi=10.1016/j.pepi.2003.11.002 }}</ref>

Intraplate earthquakes are relatively rare compared to the more familiar boundary-located interplate earthquakes. Structures far from plate boundaries tend to lack [[Earth:Seismic retrofit|seismic retrofitting]], so large intraplate earthquakes can inflict heavy damage. Examples of damaging intraplate earthquakes are the devastating 2001 Gujarat earthquake, the 2012 Indian Ocean earthquakes, the 2017 Puebla earthquake, the 1811–1812 New Madrid earthquakes, and the 1886 Charleston earthquake.<ref>{{cite journal|title=Intraplate Triggered Earthquakes: Observations and Interpretation|first1=Susan E.|last1=Hough|first2=Leonardo|last2=Seeber|first3=John G.|last3=Armbruster|url=http://bssa.geoscienceworld.org/content/93/5/2212.short|journal=Bulletin of the Seismological Society of America|publisher=Seismological Society of America|volume=101|number=3|date=October 2003|pages=2212–2221|doi=10.1785/0120020055|bibcode=2003BuSSA..93.2212H|citeseerx=10.1.1.189.5055}}</ref>

==Description==
The surface of the Earth is made up of seven primary and eight secondary [[Earth:Plate tectonics|tectonic plate]]s, plus dozens of tertiary microplates. The large plates move very slowly, owing to [[Astronomy:Convection|convection]] currents within the [[Earth:Mantle (geology)|mantle]] below the [[Earth:Crust (geology)|crust]]. Because they do not all move in the same direction, plates often directly [[Earth:Convergent boundary|collide]] or move [[Earth:Fault (geology)|laterally along each other]], a tectonic environment that makes earthquakes frequent. Relatively few earthquakes occur in intraplate environments; most occur on faults near plate margins.

Intraplate earthquakes do not occur near plate boundaries but along faults in the normally stable interior of plates.<ref>{{cite journal |last1=Yang |first1=Xiaotao |title=Seismicity of the Ste. Genevieve Seismic Zone based on Observations from the EarthScope OIINK Flexible Array |journal=Seismological Research Letters |volume=85 |issue=6 |pages=1285–1294 |doi=10.1785/0220140079 |url=https://pubs.geoscienceworld.org/ssa/srl/article/85/6/1285/315533/seismicity-of-the-ste-genevieve-seismic-zone-based|year=2014 }}</ref> These earthquakes often occur at the location of ancient failed [[Earth:Rift|rift]]s, because such old structures may present a weakness in the crust where it can slip in response to regional tectonic strain.

Compared to earthquakes near plate boundaries ([[Earth:Megathrust earthquake|megathrust earthquake]]s), intraslab earthquakes at a similar magnitude radiate more seismic energy. Thus "seismic energy" is considered a better measure for the potential macroseismic effects of an earthquake as compared to the [[Earth:Seismic moment|seismic moment]] used to calculate {{M|w}}."<ref>{{Cite journal|last1=Leyton |first1=Felipe |last2=Ruiz |first2=Javier A. |last3=Camposa |first3=Jaime |last4=Kausel |first4=Edgar |year=2009 |title=Intraplate and interplate earthquakes in Chilean subduction zone: A theoretical and observational comparison |journal=Physics of the Earth and Planetary Interiors |volume=175 |issue=1 |pages=37–46 |doi=10.1016/j.pepi.2008.03.017 }} ''citing'' Choy, G.L.; Boatwright, J.; Kirby, S., 2002. The radiated seismic energy and apparent stress of interplate and intraslab earthquakes at subduction-zone environments: Implications for seismic hazard estimation, in The Cascadia subduction zone and related subduction systems–Seismic structure, intraslab earthquakes and processes, and earthquake hazards, Open-File Report 02–328, pp. 107–114, eds Kirby, S.H.; Wang, K.; Dunlop, S., US Geological Survey, Menlo Park, CA. </ref>

==Examples==
Examples of intraplate earthquakes include those in Mineral, Virginia, in 2011 (estimated magnitude 5.8), Newcastle, New South Wales in 1989, [[Earth:New Madrid Seismic Zone|New Madrid]] in 1811 and 1812 (estimated magnitude as high as 8.6),<ref>Penick, James L. ''The New Madrid Earthquakes''. Columbia, MO: University of Missouri Press, 1981. {{ISBN|0-8262-0344-2}}</ref> the Boston (Cape Ann) earthquake of 1755 (estimated magnitude 6.0 to 6.3), earthquakes felt in {{wipe|New York City}} in 1737 and 1884 (both quakes estimated at about 5.5 magnitude), and the Charleston earthquake in South Carolina in 1886 (estimated magnitude 6.5 to 7.3). The Charleston quake was particularly surprising because, unlike Boston and New York, the area had almost no history of even minor earthquakes.

In 2001, a large intraplate earthquake devastated the region of Gujarat, India. The earthquake occurred far from any plate boundaries, which meant the region above the [[Epicenter|epicenter]] was unprepared for earthquakes. In particular, the Kutch district suffered tremendous damage, where the death toll was over 12,000 and the total death toll was higher than 20,000.

In 2017, the 24–29&nbsp;km deep magnitude 6.5 Botswana earthquake that shook eastern Botswana occurred at over 300&nbsp;km from the nearest active plate boundary.<ref name=":0">{{Cite journal|last1=Kolawole|first1=F.|last2=Atekwana|first2=E. A.|last3=Malloy|first3=S.|last4=Stamps|first4=D. S.|last5=Grandin|first5=R.|last6=Abdelsalam|first6=M. G.|last7=Leseane|first7=K.|last8=Shemang|first8=E. M.|date=2017-09-09|title=Aeromagnetic, gravity, and Differential Interferometric Synthetic Aperture Radar analyses reveal the causative fault of the 3 April 2017 Mw6.5 Moiyabana, Botswana, earthquake|journal=Geophysical Research Letters|language=en|volume=44|issue=17|pages=8837–8846|doi=10.1002/2017gl074620|issn=0094-8276|bibcode=2017GeoRL..44.8837K|s2cid=134584787 }}</ref> The event occurred in an underpopulated area of Botswana.

The 1888 earthquake in Río de la Plata was an intraplate quake,<ref>{{cite journal |last= Benavídes Sosa |first= Alberto |date= 1998 |title= Seismicidad y seismotectónica en Uruguay |journal= Física de la Tierra |url= https://revistas.ucm.es/index.php/FITE/article/viewFile/FITE9898110167A/12147  |pages= 167–186 |issue= 10 |language= es}}</ref> from reactivated faults in the  Quilmes Trough, far from the boundaries of the [[Earth:South American Plate|South American Plate]]. With a magnitude greater than 5.0 it was felt "in the cities of Buenos Aires, La Plata and other small towns and villages along the Rio de Plata coastal regions."<ref name="Rossello-2020">{{Cite journal |last1=Rossello |first1=Eduardo Antonio |last2=Heit |first2=Benjamín |last3=Bianchi |first3=Marcelo |year=2020 |title=Shallow intraplate seismicity in the Buenos Aires province (Argentina) and surrounding areas: is it related to the Quilmes Trough? |journal=Boletín de Geología |volume=42 |issue=2 |pages=31–48 |doi=10.18273/revbol.v42n2-2020002 |s2cid=219934403 |url=https://www.redalyc.org/journal/3496/349665545003/html/ |archive-url=https://web.archive.org/web/20220804031500/https://www.redalyc.org/journal/3496/349665545003/html/ |archive-date=4 August 2022 |url-status=live |doi-access=free }}</ref> The towns of Punta del Este and Maldonado in Uruguay were hit by a tsunami generated by the quake.<ref name="Rossello-2020" />

==Causes==
Many cities live with the [[Earth:Seismic risk|seismic risk]] of a rare, large intraplate earthquake. The cause of these earthquakes is often uncertain. In many cases, the causative fault is deeply buried<ref name=":0" /> and sometimes cannot even be found. Some studies have shown that quakes can be caused by fluids moving up the crust along ancient fault zones.<ref name=":0" /><ref>{{Cite journal|last1=Gardonio|first1=B.|last2=Jolivet|first2=R.|last3=Calais|first3=E.|last4=Leclère|first4=H.|date=2018-07-13|title=The April 2017 Mw6.5 Botswana Earthquake: An Intraplate Event Triggered by Deep Fluids|journal=Geophysical Research Letters|language=en|volume=45|issue=17|pages=8886–8896|doi=10.1029/2018gl078297|issn=0094-8276|url=https://hal.archives-ouvertes.fr/hal-02185463/file/2018_Gardonio_GRL.pdf|bibcode=2018GeoRL..45.8886G|s2cid=134667492}}</ref> In such circumstances, it is difficult to estimate the [[Earth:Seismic hazard|seismic hazard]] for a given city, especially if there was only one earthquake in historical times. Some progress is being made in understanding the [[Earth:Fault mechanics|fault mechanics]] driving these earthquakes.

Intraplate earthquakes may be unrelated to ancient fault zones and instead caused by deglaciation or erosion.<ref>{{cite news |last1=Shobe |first1=Charlie |title=Can Rivers Cause Earthquakes? |url=https://blogs.scientificamerican.com/observations/can-rivers-cause-earthquakes/ |access-date=26 December 2018 |work=Scientific American |date=18 December 2018}}</ref>

==Prediction==
Scientists continue to search for the causes of these earthquakes, and especially for some indication of how often they recur. The best success has come with detailed micro-seismic monitoring, involving dense arrays of [[Earth:Seismometer|seismometer]]s.  In this manner, very small earthquakes associated with a causative fault can be located with great accuracy, and in most cases these line up in patterns consistent with faulting. [[Earth:Cryoseism|Cryoseism]]s can sometimes be mistaken for intraplate earthquakes.

==See also==
* {{annotated link|Earth:New Madrid Seismic Zone}}
* {{annotated link|Earth:Saint Lawrence rift system}}

== References ==
{{Reflist}}

== Further reading ==
*Stein, S., and S. Mazzotti (2007). "Continental Intraplate Earthquakes: Science and Policy Issues", Geological Society of America, Special Paper 425.

==External links==
*[http://sprg.ssl.berkeley.edu/matt/seismo.html Intraplate Earthquakes: Possible Mechanisms for the New Madrid and Charleston Earthquakes]
*[http://www.seis.sc.edu/projects/SCSN/history/Publications/G&T_SRL_2003.pdf ''Symptomatic Features of Intraplate Earthquakes'' – PDF]
*[https://web.archive.org/web/20060508201837/http://www.rcep.dpri.kyoto-u.ac.jp/members/iio/ronbun_list/eps2002_1001.pdf ''A physical understanding of large intraplate earthquakes'' – PDF]
*[https://earthquake.usgs.gov/eqcenter/eqinthenews/2006/usslav/ Earthquake Hazards Program, USGS]
{{Clear}}

[[Category:Types of earthquake]]

ja:地震#内陸地殻内地震

{{Sourceattribution|Intraplate earthquake}}