Epicenter
 Epicenter | |
|---|---|
| Bayanai | |
| Ƙaramin ɓangare na | wuri |
Epicenter (/ˈɛpɪˌsɛntər/), epicentre, ko epicentrum[1] a fannin ilimin nazarin girgizar ƙasa (seismology), shi ne wurin da ke saman Duniya kai tsaye a bisa hypocenter ko focus, wato wurin da girgizar ƙasa ko kuma fashewar wani abu a ƙarƙashin ƙasa ta samo asali.
Ƙaddamarwa
[gyara sashe | gyara masomin]
Babbar manufar seismometer ita ce gano wuraren da girgizar ƙasa ta samo asali, wato epicenter. Manufa ta biyu ita ce tantance “girman” ko ƙarfin girgizar ƙasa (magnitude), wanda dole ne a ƙididdige shi bayan an gano ainihin wurin da girgizar ƙasar ta faro.
An ƙera seismographs na farko ne domin su ba da fahimtar alkiblar motsin farko da ke faruwa sakamakon girgizar ƙasa. Seismograph na kwaɗon Sinawa[2]yana sauke ƙwallonsa zuwa kusan alkiblar da ke nuna inda girgizar ƙasar ta fito, idan aka yi la’akari da cewa an samu bugun farko mai ƙarfi zuwa waje (strong positive pulse).
Yanzu mun san cewa motsin farko na iya kasancewa ta kusan kowace irin alkibla, gwargwadon nau’in tsagewar da ta fara haifar da girgizar ƙasar (focal mechanism).[3]
Gyaran farko da ya ba da damar gano wurin da girgizar ƙasa ta faro cikin ƙarin daidaito shi ne amfani da ma’aunin lokaci (time scale). Maimakon kawai lura ko yin rikodin motsin pendulum, an zana sauye-sauyen matsayi (displacements) a kan wani jadawali mai motsi, wanda wata na’urar agogo (clock mechanism) ke tafiyar da shi.
Wannan shi ne seismogram na farko, wanda ya ba da damar tantance lokacin da motsin ƙasa na farko (ground motion) ya faru cikin cikakken daidaito, tare da yin cikakken zane na sauran motsin ƙasar da suka biyo baya.
Daga seismogram na farko, kamar yadda aka nuna a hoton, an lura cewa zanen rikodin ya kasu zuwa manyan sassa biyu. Tsuntsuwar girgizar ƙasa ta farko da ta iso ita ce P wave, sannan S wave ta biyo bayanta ba da daɗewa ba. Da yake an san bambancin saurin yaɗuwar waɗannan raƙuman girgizar ƙasa, ya zama abu mai sauƙi a ƙididdige nisan da girgizar ƙasar take daga wurin da aka yi rikodin ta.[4]
Ɗaya daga cikin seismograph zai ba da nisa, amma ana iya tsara hakan a matsayin da'ira, tare da adadi mara iyaka na yiwuwar. Seismographs guda biyu za su ba da da'irori biyu masu haɗuwa, tare da wurare biyu masu yiwuwa. Sai kawai tare da seismograph na uku za a sami ainihin wuri.[4]
Yanayin girgizar ƙasa na zamani har yanzu yana buƙatar akalla seismometers uku. Wataƙila, akwai da yawa, suna samar da jerin girgizar ƙasa. An jaddada shi ne a kan daidaito tunda ana iya koya da yawa game da injin kuskure da Hadarin girgizar ƙasa, idan za'a iya ƙayyade wuraren da ke cikin kilomita ɗaya ko biyu, don ƙananan girgizar ƙasar. Don wannan, shirye-shiryen kwamfuta suna amfani da tsari na maimaitawa, wanda ya haɗa da 'tsinkaya da gyara' algorithm.[5] Hakanan, ana buƙatar samfurin mai kyau na tsarin saurin ɓawon burodi na gida: saurin girgizar ƙasa ya bambanta da ilimin ƙasa na gida. Ga raƙuman ruwa na P, dangantakar da ke tsakanin saurin da yawa na matsakaici an ƙayyade shi a cikin Dangantakar Gardner.
Lalacewar ƙasa
[gyara sashe | gyara masomin]Kafin lokacin kayan aiki na lura da girgizar ƙasa, an yi tunanin cibiyar ita ce wurin da mafi girman lalacewa ya faru, amma fashewar lalacewar ƙasa na iya zama mai tsawo kuma ya bazu lalacewar farfajiyar a duk yankin fashewa. A matsayin misali, a cikin girgizar ƙasa ta Denali ta 7.9 ta 2002 a Alaska, cibiyar ta kasance a ƙarshen yammacin fashewar, amma mafi girman lalacewa ya kasance kusan kilomita 330 km (210 mi) (210 daga ƙarshen gabas.[6] Gudun zurfin girgizar ƙasa da ke faruwa a cikin ɓawon burodi mafi yawa daga kilomita 2 zuwa 20 (1.2 zuwa 12.4 . Girgizar ƙasa a ƙasa da 20 km (12 mi) km (12 ba ta da yawa yayin da girgizar ƙasa ta yankin subduction na iya samo asali a zurfin fiye da 600 km (370 mi) . [7]
Tsakanin tsakiya
[gyara sashe | gyara masomin]A lokacin girgizar ƙasa, Raƙuman ruwa na girgizar ƙasa suna yaduwa a kowane bangare daga munafunci. Inuwa ta girgizar ƙasa tana faruwa a gefen duniya daga cibiyar girgizar kasa saboda ruwan da ke waje na duniya yana karkatar da tsayi ko matsin lamba (P raƙuman ruwa) yayin da yake shan raƙuman raƙuman ƙasa (S raƙuman). A waje da yankin inuwa na girgizar ƙasa, ana iya gano nau'ikan raƙuman ruwa guda biyu, amma saboda saurin su daban-daban da hanyoyin su ta Duniya, suna zuwa a lokuta daban-daban. Ta hanyar auna bambancin lokaci a kan kowane seismograph da nesa a kan jadawalin lokacin tafiya wanda raƙuman P da raƙuman S suna da rabuwa iri ɗaya, masu ilimin ƙasa na iya lissafin nesa zuwa cibiyar girgizar ƙasa. Wannan nisan ana kiransa nisan tsakiya, wanda aka auna a cikin ° (matakan) kuma ana nuna shi a matsayin Δ (delta) a cikin seismology. Dokar Laska ta kwarewa tana ba da kusanci na nesa mai tsakiya a cikin kewayon 2,000-10,000 km.
Da zarar an lissafa nisan daga cibiyar daga akalla tashoshin auna girgizar ƙasa guda uku, ana iya samun ma'anar, ta amfani da trilateration.
Epicentral distance is also used in calculating seismic magnitudes as developed by Richter and Gutenberg.[8][9]
Rashin kuskure
[gyara sashe | gyara masomin]Ma'anar da lalacewar ta fara ana kiranta da mayar da hankali ga girgizar kasa. Rushewar kuskuren ya fara ne a mayar da hankali sannan ya fadada tare da kuskuren. Rushewar ta tsaya inda damuwa ta zama bai isa ba don ci gaba da karya kuskuren (saboda duwatsu sun fi karfi) ko kuma inda fashewar ta shiga kayan ductile.[7] Girman girgizar ƙasa yana da alaƙa da jimlar yankin fashewar ta.[7] Yawancin girgizar ƙasa ƙananan ne, tare da girman fashewa ƙasa da zurfin mai da hankali don haka fashewar ba ta karya farfajiyar ba, amma a cikin girma, girgizar kasa mai lalacewa, fashewar farfajiya sun zama ruwan dare.[7] Rashin fashewa a cikin manyan girgizar ƙasa na iya kaiwa sama da kilomita 100 km (62 mi) (62 . [7] Lokacin da kuskuren ya fashe a gefe ɗaya (tare da cibiyar a ko kusa da ƙarshen kuskuren) raƙuman ruwa sun fi karfi a gefe ɗaya tare da kuskurensa.[10]
Cibiyar Macroseismic
[gyara sashe | gyara masomin]Cibiyar macroseismic ita ce mafi kyawun kimantawa game da wurin da aka samo ba tare da bayanan kayan aiki ba. Ana iya kimanta wannan ta amfani da bayanai masu ƙarfi, bayani game da foreshocks da aftershocks, ilimin tsarin kuskuren gida ko karin bayanai game da irin wannan girgizar ƙasa. Ga girgizar ƙasa ta tarihi waɗanda ba a rubuta su da kayan aiki ba, ana iya ba da cibiyar macroseismic kawai.
Magana
[gyara sashe | gyara masomin]Kalmar ta samo asali ne daga sunan Neo-Latin epi, [11] Latinization na tsohuwar kalmar Helenanci ἐπίκεντρος (epikentros), "suna zama a wani wuri mai mahimmanci, wanda ke kan tsakiya", daga ἐπί (epi) "a, a kan, a" da κέντρον (kentron) "tsakiya". Kalmar ta samo asali ne daga Masanin ilimin girgizar ƙasa na Irish Robert Mallet .
Hakanan ana amfani dashi don nufin "cibiyar aiki", kamar yadda a cikin "Tafiye-tafiye ya ƙuntata a lardin kasar Sin da ake zaton shine cibiyar barkewar SARS".Garner's Modern American Usage ya ba da misalai da yawa na amfani wanda ake amfani da "epicenter" don nufin "cibiyar". Garner kuma yana nufin wani labarin William Safire wanda Safire ya nakalto wani masanin ilimin ƙasa kamar yadda yake danganta amfani da kalmar ga "ƙwarewar ƙarya daga ɓangaren marubutan da aka haɗa da ilimin kimiyya daga ɓangaren masu gyara kwafin". Garner ya yi hasashen cewa waɗannan kuskuren na iya zama kawai "bayanan kwatanci na mahimman bayanai na yanayin da ba a daidaita ba kuma mai iya lalatawa".
Manazarta
[gyara sashe | gyara masomin]- ↑ Oxford English Dictionary: "The point over the centre: applied in Seismol. to the outbreaking point of earthquake shocks."
- ↑ "Chinese Seismograph". Archived from the original (jpg) on 2019-09-16. Retrieved 2023-08-11.
- ↑ "USGS Earthquake Hazards Program". Archived from the original on 2005-12-22. Retrieved 2023-09-06.
- 1 2 "How Can I Locate the Earthquake Epicenter?".
This technique is called "trilateration."
- ↑ "USGS Earthquake Hazards Program". Archived from the original on 2005-12-18. Retrieved 2023-09-06.
- ↑ Fuis, Gary; Wald, Lisa. "Rupture in South-Central Alaska – The Denali Fault Earthquake of 2002". United States Geological Survey. Retrieved 2008-04-20.
- 1 2 3 4 5 Cite error: Invalid
<ref>tag; no text was provided for refs named "JordanGrotzinger2012". - ↑ Tyler M. Schau (1991). "The Richter Scale (ML)". United States Geological Survey. Archived from the original on 2016-04-25. Retrieved 2008-09-14.
- ↑ William L. Ellsworth (1991). "Surface-Wave Magnitude (Ms) and Body-Wave Magnitude (mb)". United States Geological Survey. Archived from the original on 2009-02-02. Retrieved 2008-09-14.
- ↑ "What is Directivity?". United States Geological Survey. Retrieved 2018-07-01.
- ↑ "epicenter". Merriam-Webster Dictionary. 2009. Retrieved 2009-10-19.
