Observatorio Vulcanológico y Sismológico de Costa Rica

URI permanente para esta comunidadhttp://10.0.96.45:4000/handle/11056/14933

El Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORI) de la Universidad Nacional, es un instituto de investigación universitaria dedicado a la investigación de los volcanes, los sismos y otros procesos tectónicos, con el propósito de encontrar aplicaciones útiles a la sociedad que ayuden a mitigar los efectos adversos de esos fenómenos al desarrollo económico y social. Se trata de un observatorio, por cuanto una cantidad considerable de su esfuerzo va orientada a documentar la actividad sísmica, volcánica y la deformación cortical que, a su vez, retroalimenta a las actividades investigativas propias de un instituto de investigación universitaria.

Contáctenos:

Página web: www.ovsicori.una.ac.cr

Correo: ovsicori@una.cr

Teléfono: (506) 2562 4001 / (506) 2261 0611 / (506) 2261 0781

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Correlation between the age of the subducting Cocos Plate and the geometry of the Wadati-Benioff zone under Nicaragua and Costa Rica.
(Universidad Nacional, Costa Rica, 1995) Protti, Marino; Güendel, Federico; McNally, Karen
High- resolution seismicity data from Costa Rica and southern Nicaragua have been used to image the geometry of the Wadati-Benioff zone under southern Central America. The data include 9,514 events with computed horizontal and vertical errors smaller than 4 and 5 km respectively. We found that under the Nicaragua- Costa Rica border the Wadati- Benioff zone contorts (from steep to shallow dip angles, northwest to southeast) but does not show evidence of a brittle tear, as postulated by others. Further to the southeast-northeast from Puerto Caldera- the Wadati-Benioff zone does, however, show a tear (the Quesada Sharp Contortion) at intermediate depths (h >70 km). Overall the dip angle of the Wadati-Benioff zone decreases from 84° under Nicaragua to 60° under central Costa Rica. The maximum depth of interaplate Wadati-Benioff zone earthquakes also decreases from northwest (-200 km under Nicaragua) to southeast (-125 km under central Costa Rica). In southern Costa Rica, east of 83°55 W, we find no evidence of the Wadati-Benioff zone below 50 km. This geometry of the Wadati-Benioff zone and other tectonic features related to the subduction of the Cocos plate beneath the Caribbean plate have been integrated into a model that correlates them with along- trench variations in age of the subducted Cocos plate. These tectonic featuresare (1) the shallowing of the Middle America Trech bathymetry from northwest to southeast, (2) differences in coupling between Cocos and Caribbean plates, (3) the termination of the Central America Volcanic Chain in central Costa Rica, and (4) distinct stress field variations on the overriding Caribbean plate. The subduction of the Cocos Ridge under southern Costa Rica is partially responsible for somo of these features (shallowing of the Middle America Trench in southern Costa Rica) and for the high uplift rates of the outer arc, However, since the presence of the Panama Fracture Zone limits the subducted extension of the Cocos Ridge to less that 100 km from the trench, we propose that the overall geometry of the Wadati- Benioff zone is controlled by abrupt along trench changes in the age of the subducted Cocos plate.
Seafloor structural observations, Costa Rica accretionary prism
(1996-04-15) McAdoo, Brian G.; Orange, Daniel L.; Silver, Eli; McIntosh, Kirk; Abbott, Lon; Galewsky, Joseph; Kahn, Leslie; Protti, Marino
By studying seafloor morphology we can make associations between near surface defornation, fluid flow and the overakk structural framework of accretionary prisms. In February, 1994 a DS/RV ALVIN program to the Costa Rica accretionary prism investigated the relationship of fluid seepage and sediment deformation by using the distribution of chemosynthetic communities and heat flow anormalies as indicators of fluid flow. The active normal faults that cut the hemipelagic section on the Cocos plate may provide conduits for fluids that cause the regional heat flow to be extremely low. These normal faults intersect the toe of the prism at an oblique angle, creating localized regions of increased deformation. Positive heat flow anormalies observed at the deformation. Positive heat flow anormalies observed at the deformation front indicate of flow, however, we discovered ni seep communities indicative of focused flow. The seaward-most seep communities discovered are in a region of active out-of-sequence thrusts that cut a sediment apron which covers the complex to within 3 km of the prism toe. Vents occur consistently at the base of the fault scarps. Dives in a mud diapir show extensive seep communities, pock marks, and authigenic carbonates. Evidence of a fluid release is on the crest which implies a low viscosity fluid migrating upward in the center of the structure. Normal faults on the upper slope can be seen in cross- section in the walls of a submarine canyon. The faults cut the slope apron and displace the seafloor, actively maintaining the critical taper of the prism.
The March 25, 1990 (Mw=7.0 Ml=6.8) earthquake at the entrance of the Nicoya Gulf, Costa Rica: its prior activity, foreshocks, aftershocks and triggered seismicity
(1995-10-10) Protti, Marino; McNally, Karen; Pacheco, Javier; González, Victor; Montero, Carlos; Segura, Juan; Brenes, Jorge; Barboza, Vilma; Malavassi, Eduardo; Güendel, Federico; Simila, Gerald; Rojas, Daniel; Velasco, Aaron; Mata, Antonio; Schillinger, Walter
On March 25, 1990 a large earthquake( Mw=7.0, ML=6.8) occurreda t the entranceo f the Nicoya Gulf, CostaR ica, at 1322:55.6U TC, producingc onsiderabled amagei n centralC osta Rica andg eneratingm uchi nteresta boutw hethero r not the Nicoya seismicg ap (Nishenko,1 989) had broken.T he local country-wides eismographince tworkr ecorded6 yearso f activityp rior to thisl argee arthquake1, 6 hourso f foreshockst,h e mainshocka, ndi ts aftershocksT.h is networki s operatedjo intly by the CostaR ica Volcanologicala nd SeismologicaOl bservatorya t the National University( OVSICORI-UNA), andt he CharlesF . RichterS eismologicaLl aboratorya t the Universityo f California,S antaC ruz (CFRSL-UCSC).W e obtainedh igh resolutionlo cations from thisn etworka ndl ocatedt hem ainshocka t 9ø38.5'N,8 4ø55.6'W( depthi s 20.0 km) andt he largestf oreshock(M w=6.0,M arch2 5, 1990,a t 1316:05.8U TC) at 9ø36.4'N,8 4ø57.1'W( depth is 22.4 km). We find that the aftershockz one abutst he southeasbt oundaryo f the Nicoya seismic gap, suggestingth at the seismicg ap did not rupture.S incet he installationo f the local networki n April 1984 to March 24, 1990, nearly 1900 earthquakews ith magnitudesfr om 1.7 to 4.8 (318 with magnitude3 .0 or larger)h aveb eenl ocateda t the entranceo f the Nicoya Gulf, one of the mosta ctiver egionsi n CostaR ica. The March 25 earthquakeo ccurreda t the northweste dgeo f this region,w herea sequencoe f foreshockbs egan1 6 hoursp rior to the mainshockT. he spatialtemporadl istributiono f aftershockasn dd irectivitya nalysiso f the mainshockru pturep rocess usingt eleseismicre cordsb othi ndicatea southeasptr opagatingru pture.T he mainshockru ptured ana speriotyf approximat6e0ly0k m2 ofa reaw, itht hisa reae xpanditnog4 000k m2 afte7r days. We presenet videnceth ats uggesttsh att her uptureda sperityis producedb y the subductioonf a seamountI.n versiono f teleseismicb roadbanda ndl ong-periodP and SH wavesy ieldsa thrust faultingm echanismw ith the shallowp lanes triking2 92ø , dipping2 6ø , andw ith a rakeo f 88ø , in agreemenwt ith the subductiono f the Cocosp lateu ndert he Caribbeanp late.L ocal first motions for the largestf oreshocka ndt he mainshocka greew ith thiss olutionW. e alsop resente vidence suggestintgh at the March 25, 1990,e arthquaketr iggereda ndr eactivateds everals eismics warmsin centralC ostaR ica andt emporallyd ecreasedth e activityi n the epicentraal reao f the July 3, 1983 (Ms=6.2), P6rez Zeled6n earthquake.

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