1977 San Juan earthquake: Difference between revisions
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==Earthquake== |
==Earthquake== |
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The earthquake consisted of two sub-events, separated by about 20 seconds. The observed [[focal mechanism]] was [[Fault (geology)#Dip-slip faults|reverse faulting]], on a north-south trending structure. From the mainshock alone, it was not possible to decide whether the fault responsible [[Strike and dip|dipped]] to the west or east. Analysis of the [[aftershock]] sequence suggests that two separate faults moved during the earthquake, the earlier event on a segment to the north and the later one to the south. The dip of the faults involved remains unclear. |
The earthquake consisted of two sub-events, separated by about 20 seconds, treated by some seismologists as foreshock and mainshock.<ref name="Langer_&_Hartzell_1996">{{Cite journal |last=Langer |first=C.J. |last2=Hartzell |first2=S. |year=1996 |title=Rupture distribution of the 1977 western Argentina earthquake |journal=Physics of the Earth and Planetary Interiors |volume=94 |issue=1–2 |pages=121–132 |doi=10.1016/0031-9201(95)03080-8}}</ref> The observed [[focal mechanism]] was [[Fault (geology)#Dip-slip faults|reverse faulting]], on a north-south trending structure. From the mainshock alone, it was not possible to decide whether the fault responsible [[Strike and dip|dipped]] to the west or east. Analysis of the [[aftershock]] sequence suggests that two separate faults moved during the earthquake, the earlier event on a segment to the north and the later one to the south. The dip of the faults involved remains unclear.<ref name="Regnier_etal_1992">{{Cite journal |last=Regnier |first=M. |last2=Chatelain |first2=J.L. |last3=Smalley Jr |first3=R. |last4=Chiu |first4=J.-M. |last5=Isacks |first5=B.L. |last6=Araujo |first6=M. |year=1992 |title=Seismotectonics of Sierra Pie de Palo, a basement block uplift in the Andean Foreland of Argentina |url=https://www.researchgate.net/profile/Jean-Luc_Chatelain/publication/236144911_Seismotectonics_of_Sierra_Pie_De_Palo_a_basement_block_uplift_in_the_Andean_foreland_of_Argentina/links/0deec5165751c3cbaa000000/Seismotectonics-of-Sierra-Pie-De-Palo-a-basement-block-uplift-in-the-Andean-foreland-of-Argentina.pdf |journal=Bulletin of the Seismological Society of America |volume=82 |issue=6 |pages=2549–2571}}</ref> |
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There was no surface rupture associated with the earthquake and it is example of a [[blind thrust earthquake]] on thrust faults underlying the Pie de Palo range.<ref name="Meigs_&_Nabelek_2010">{{Cite journal |last=Meigs |first=A.J. |last2=Nabelek |first2=J. |year=2010 |title=Crustal‐scale pure shear foreland deformation of western Argentina |journal=Geophysical Research Letters |volume=37 |issue=11 |doi=10.1029/2010GL043220}}</ref> |
There was no surface rupture associated with the earthquake and it is example of a [[blind thrust earthquake]] on thrust faults underlying the Pie de Palo range.<ref name="Meigs_&_Nabelek_2010">{{Cite journal |last=Meigs |first=A.J. |last2=Nabelek |first2=J. |year=2010 |title=Crustal‐scale pure shear foreland deformation of western Argentina |journal=Geophysical Research Letters |volume=37 |issue=11 |doi=10.1029/2010GL043220}}</ref> |
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==References== |
==References== |
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Revision as of 19:18, 8 February 2020
  San Juan  | |
| UTC time | 1977-11-23 09:26:26 |
|---|---|
| ISC event | 690743 |
| USGS-ANSS | ComCat |
| Local date | 23 November 1977 |
| Local time | 06:26:26 |
| Magnitude | 7.4 Ms [1] |
| Depth | 17 km (11 mi) [2] |
| Epicenter | 31°05′S 67°47′W / 31.08°S 67.78°W [2] |
| Max. intensity | IX (Violent) [3] |
| Casualties | 65 deaths |
The 1977 San Juan earthquake, also known as Caucete earthquake, took place in the province of San Juan, Argentina, on 23 November at 09:26:26 AM. It measured 7.4 on the surface wave magnitude scale,[1] and had a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale.
The earthquake caused fatalities and severe damage to buildings throughout the province, especially in the city of Caucete, where at least 65 people died. It also caused slight damage in the north of the Greater Mendoza metropolitan area.
The effects of the earthquake were felt as far away as Buenos Aires, where people were awakened that Wednesday by the tremor. People left their houses at dawn in panic at the Argentinian capital, located at 1,000 km to the East South East.[citation needed]
Tectonic setting
San Juan Province lies in an area where the South American Plate is affected by flat-slab subduction of the underlying Nazca Plate, the so-called Pampean flat-slab. The very shallow angle leads to a much greater degree of coupling between the subducting and overriding plates. The increased coupling leads to shortening of the crust of the South American Plate, causing active thrust tectonics and rapid uplift, forming the Sierras Pampeanas. The Pie de Palo range is one of the active structures, interpreted to be controlled by major thrust faults.[4]
Earthquake
The earthquake consisted of two sub-events, separated by about 20 seconds, treated by some seismologists as foreshock and mainshock.[5] The observed focal mechanism was reverse faulting, on a north-south trending structure. From the mainshock alone, it was not possible to decide whether the fault responsible dipped to the west or east. Analysis of the aftershock sequence suggests that two separate faults moved during the earthquake, the earlier event on a segment to the north and the later one to the south. The dip of the faults involved remains unclear.[6]
There was no surface rupture associated with the earthquake and it is example of a blind thrust earthquake on thrust faults underlying the Pie de Palo range.[7]
References
- ^ a b Keefer, D. K.; Youd, T. L. (1994), "Liquefaction during the 1977 San Juan Province, Argentina earthquake (Ms = 7.4)", Engineering Geology, 37 (3–4): 211–233, doi:10.1016/0013-7952(94)90057-4
- ^ a b Utsu, T. R. (2002), "A List of Deadly Earthquakes in the World: 1500–2000", International Handbook of Earthquake & Engineering Seismology, Part A, Volume 81A (First ed.), Academic Press, p. 683, ISBN 978-0124406520
- ^ National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
- ^ Siame, L.L.; Sébrier, M.; Bellier, O.; Bourlès, D.; Costa, C.; Ahumada, E.A.; Gardini, C.E.; Cisneros, H. (2015). "Active basement uplift of Sierra Pie de Palo (Northwestern Argentina): Rates and inception from 10Be cosmogenic nuclide concentrations". Tectonics. 34: 1129–1153. doi:10.1002/2014TC003771.
- ^ Langer, C.J.; Hartzell, S. (1996). "Rupture distribution of the 1977 western Argentina earthquake". Physics of the Earth and Planetary Interiors. 94 (1–2): 121–132. doi:10.1016/0031-9201(95)03080-8.
- ^ Regnier, M.; Chatelain, J.L.; Smalley Jr, R.; Chiu, J.-M.; Isacks, B.L.; Araujo, M. (1992). "Seismotectonics of Sierra Pie de Palo, a basement block uplift in the Andean Foreland of Argentina" (PDF). Bulletin of the Seismological Society of America. 82 (6): 2549–2571.
- ^ Meigs, A.J.; Nabelek, J. (2010). "Crustal‐scale pure shear foreland deformation of western Argentina". Geophysical Research Letters. 37 (11). doi:10.1029/2010GL043220.
External links
- Listado de Terremotos Históricos (in Spanish) — Instituto Nacional de Prevención Sísmica
- The International Seismological Centre has a bibliography and/or authoritative data for this event.