SUN FAƊI INDA GIRGIZAR ƘASA ZA TA FARA

Hasashen girgizar ƙasa na dogon lokaci yana ba da yiwuwar cewa wani sashe na layin tsagewar ƙasa (fault) zai karye cikin wani lokaci. Ga sassan tsakiya da kudu na yankin layin Hinagu, a tsakiyar Kyushu, Japan, ƙiyasin hukuma ya kai har 6% da 16% cikin shekaru 30. Abin da irin waɗannan hasashe ba sa taɓa faɗi shi ne a wane wuri a kan layin karyewa (rupture) za ta fara.

Ma’aunin matsi

Masana girgizar ƙasa suna ƙirga girgizar ƙasa gwargwadon girmanta. Adadin N na girgizar ƙasa masu ƙarfi (magnitude) M ko sama da haka yana bin dokar Gutenberg–Richter, log₁₀N = a − bM. Gangaren layin, wanda ake kira b-value (ƙimar b), yana ƙayyade gwargwadon ƙananan girgizar ƙasa da manya. Gwaje-gwaje a ɗakin gwaji da nazarce-nazarce kan ɓawon Duniya sun nuna cewa yana raguwa yayin da matsi (stress) — nauyin da ke matse dutse da kuma tura sassansa gefe-gefe — ke ƙaruwa. Idan aka zana shi a taswira bisa wuri da lokaci, sai ya zama ma’aunin matsi: ƙananan ƙimomin b suna nuna sassan layin da suka fi ɗaukar nauyi.

Wannan ra’ayi yana da tarihi. A Parkfield, California, wata taswirar b-value da aka buga shekaru bakwai kafin girgizar ƙasa mai ƙarfin 6.0 ta 2004 ta nuna sashen da zai zame. Ba ta faɗi inda karyewar za ta fara ba, kuma marubutan taswirar sun kira ainihin wurin farawar abin mamaki. Ga wasu manyan girgizar ƙasa da yawa, sai bayan aukuwarsu aka lura da ƙarancin b-value, lokacin da ya yi latti a gwada shi.

Murabba’i a kan taswira, a 2019

A Afrilu 2016, jerin girgizar ƙasa na Kumamoto — mai ƙarfin 6.5, sannan 6.4, sannan 7.3 — ya karya sashen arewa na yankin layin Hinagu da yankin layin Futagawa da ke maƙwabtaka da shi. Sassan tsakiya da kudu na Hinagu ba su karye ba.

K. Z. Nanjo da abokan aikinsa sun zana taswirar b-value daga Janairu 2017 zuwa Maris 2019, ta amfani da kundin bayanan Hukumar Yanayi ta Japan (Japan Meteorological Agency). Ko’ina a kan yankunan layukan biyu, b ya ƙaru bayan 2016, alamar cewa an saki matsi. Ko’ina sai a wuri ɗaya: tsakiyar yankin layin Hinagu, inda ya ragu. Wasu alamu biyu sun nuna wuri ɗaya: yadda girgizar bayan-fage (aftershocks) ke ƙarewa a can, da wani samfurin zamewar a hankali (slow slip) da ta biyo bayan 2016, wadda ta tsaya kusa da wurin ba tare da ta kai shi ba.

A 2019, ƙungiyar ta buga wannan yanki — murabba’i mai tsayi (rectangle) da ya ratsa 130.6–130.8°E da 32.5–32.6°N — a matsayin wurin da karyewa ta gaba ta fi yiwuwa ta fara, kuma ta sanar da shi a wani taron manema labarai a gwamnatin lardin Kumamoto.

Taswirorin b-value kafin 2016 (a) da daga Janairu 2017 zuwa Maris 2019 (b): shuɗi yana nufin ƙananan ƙimomin b. Murabba’i ja shi ne yankin da aka ambata a 2019; taurari ja suna nuna girgizar ƙasa na 2026. — Hoto na 2, Nanjo da abokan aiki (2026), arXiv:2610.39393.

Shekaru bakwai bayan haka

A ranar 28 ga Yuli 2026, girgizar ƙasa mai ƙarfin 7.1 ta afka wa sashen tsakiya na yankin layin Hinagu kuma ta tsaga saman ƙasa. Washegari kai tsaye, ƙungiyar ta nuna taswirarta ta 2019 ga Kwamitin Binciken Girgizar Ƙasa na Japan (Earthquake Research Committee).

A kan taswirar, cibiyar girgizar a saman ƙasa (epicentre) — wurin da ke saman ƙasa daidai sama da inda karyewar ta fara — tana ɗan wajen murabba’in, kilomita 2.9 daga gefensa na arewa: ƙasa da radiyas na kilomita 5 da kowane wuri a taswirar ke tattara girgizar ƙasarsa a cikinsa, don haka yana cikin iyakar kaifin taswirar. Amma taswira tana haɗa dukkan zurfafa har zuwa kilomita 25, alhali karyewa tana farawa ne a wuri ɗaya a ƙarƙashin ƙasa. A wani yanki a tsaye (vertical slice) da aka yanka tare da layin, yankin ƙarancin b yana miƙewa zuwa ƙasa, kuma wurin farawar 2026, a zurfin kilomita 16, yana cikinsa, inda b yake 0.6–0.7. A cikin samfurori na farko guda biyu masu zaman kansu, yankin babbar zamewa — sama da mita 1.2 — ya ratsa wurin da aka ambata a 2019.

Ƙananan ƙimomin suna nan har zuwa gab da girgizar ƙasar. Bayan haka, b a kewayen wurin farawar ya tashi zuwa 0.9–1.2, kamar yadda ake tsammani da zarar an saki matsi. A sanin marubutan, wannan shi ne wurin farawar babbar girgizar ƙasa na farko da aka buga tun kafin aukuwarta.

Ƙimomin b a wani yanki a tsaye tare da layin Hinagu: kafin 2016 (a), gab da girgizar ƙasa ta 2026 (b) da bayanta (c). Girgizar mai ƙarfin 7.1 ta fara a alamar kilomita 0 a kan yankin, a zurfin kilomita 16, cikin wani yanki shuɗi na ƙarancin b. — Hoto na 4, Nanjo da abokan aiki (2026), arXiv:2610.39393.

Ɗan takara na gaba

Yankin a tsaye yana nuna wani yankin ƙarancin b, kimanin kilomita 20 kudu maso yamma da inda karyewar 2026 ta fara, daidai inda babbar zamewarta ta ƙare. Yana kan wani lanƙwasa a layin, inda layin ke canza alƙibla — lanƙwasar da wani binciken fage ya riga ya zana kafin girgizar ƙasar. Jerin girgizar 2016 ma ya fara ne a wani lanƙwasa mai ƙananan ƙimomin b. Wannan yanki ya ci gaba da samun ƙananan ƙimomin b tun 2000, a cikin jerin biyun: babu ɗayansu da ya saki matsinsa. Kamar a 2019, marubutan sun ambace shi a matsayin wurin da karyewa ta gaba ta fi yiwuwa ta fara.

Daga can, karyewa za ta iya gudu zuwa kudu maso yamma, ƙarƙashin Tekun Yatsushiro. Girgizar ƙasa ba ta yawaita a can sosai har a iya auna b, don haka ƙungiyar ta lissafa yadda zamewar 2026 ta sauya matsi a kan waɗannan layuka. Amsar: ta tura su kusa da karyewa, da mafi girman ƙima na 0.9 zuwa 1.7 bar a ƙarshensu na arewa maso gabas, gwargwadon samfurin. Waɗannan su ne ainihin layukan da ƙiyasin hukuma ya riga ya ba yiwuwa mafi girma — har zuwa 16% cikin shekaru 30.

Wuri, ba rana ba

“Girgizar ƙasa ɗaya ba za ta iya nuna yadda wata hanya ke aiki da kyau ba,” in ji marubutan. Domin a yi mata hukunci, dole ne a yi amfani da matakai iri ɗaya a kan wasu layuka, tare da rubuta kowane zaɓi kafin girgizar ƙasar ta zo. Bayanan sun riga sun wanzu: hanyoyin na’urori (networks) a Japan, California, Chile, Italiya da Türkiye suna naɗar har da ƙananan girgizar ƙasa, shekara bayan shekara. Yankin da aka ambata a 2019 ya jira girgizar ƙasarsa shekaru bakwai, kuma babu wani abu a cikin b-value da ke faɗin yaushe ta gaba za ta zo. Abin da yake bayarwa shi ne wurin da za a sa ido, domin a iya sake duba shirin ko-ta-kwana a can kafin girgizar ƙasar maimakon bayanta.