Lirnghing leh Mizoram

Tunlai chu kan ṭhenawm state-te chauhin an tawn tur emaw kan tih lirnghing hi Mizoramin kan tawng ve ta zeuh zeuh mai. Engnge a nih tak? Eng vanga lo kal nge? Engtinnge kan khawvel hian kan tawn dan tak tihte hi hriat kan chak em em ṭhin? He thuziak hmang hian zawhna tam tak chhan kan tum dawn a ni. 

Lirnghing hi ‘one of the world’s most unpredictable natural phenomenon since time immemorial’  tiin sawi a ni fo a. A awmzia tlang­pui chu, thil sawi lawk theih loh khawvelin a ken telte zinga mi tihna a ni. Mi thiam (scientist) kan tihte hian kum 1960 chho aṭang khan lir a nghinin, lei chet dan hriat tumin mathematical modeling hrang hrang an bei ṭan a, chu chu ‘Ground Motion Prediction Equations’ tih phuahin lirnghing kal ta te chanchin lain, a leilung, a thuk zawng, a len leh tet dan/ a zau zawng (magnitude), a lei chhet dan (amplitude) leh a dang dangte hmangin he equation hi hmun hrang hrang tan an siam chhuak tawh ṭhin a. Mahse zaa za a dik hi chu a awm thei lo. 

An model reng reng hian ‘degree of accuracy/ probability’ (dik theih chin/ rin thu) a nei zel a. A chhan chu, a tira sawi tawh ang khan ‘thil sawi lawk theih loh, khawvelin a ken tel si’ a nih vang a ni.

Engnge ground motion chu?

Ground motion chu lei che tihna a ni mai a. Civil Engineer-te chuan Magnitude Mw 4.0 chin hi an ngai pawimawh em em a, chu chu ‘strong ground motions’ an ti. Magnitude Mw 4.0 chin kan han tih chhan chu, hemi chin hian a thil che, chak tak (energy wave) pek chhuah a tam tawkin kan in leh lo, kopang leh Civil Engineering Structures-te khawih che thei chin a nih vang a ni. 

Hemi aia hniam hi chuan kan in leh lote a khawih pha loa rin a ni. Magnitude kan tih hian, tunlai kan hriat lar em em fault line (lei chhung rila lei leh lei inzawmna lai fel tawk lo) kan tihte kha leilung insang mar (stress) nasa takin a nek char char a, a zawh tawk aia nasa a thlen khan a puak keh ta ṭhin a, chu chuan thil che (energy wave) a rawn tichhuak (release) ta ṭhin a, chu thil che (energy wave) rawn chhuak a zir khan, a magnitude kha a sang ta ṭhin a ni. 

Energy a tam leh a magni­tude rawn sangin, a ground motion a rawn sang ta ṭhin a, a hlauhawm tawlh tawlh te pawh a tih theih ang chu. Mahse a magnitude inang reng pawh hi, a in tanna hmun, a thuk zawng, a leilung, a nghing hun a zirte hian a leilung chet dan (ground motion) chu a danglam nasa thei em em a ni. 

Entirnan, hman kum lawk khan Mw 6.8 Gangtok-ah leh Manipur-ah a nghing a. Gangtok kha ruah sur duh hunlai a nghing niin, an ram pawh kan ram ang deuh, tlang ram a ni a; in chim, lung lum, leimin, lung lumin in a tihchhiat a tam em em a ni. Nimahsela, Manipur chu khaw ro laia nghing a nih mai bakah, a nghingna hmun kha tlang ram a nih loh avangin in chhia pawh a tlemin, leimin, lunglum report kha a awm lo tluk a ni. 

Tunlaia Mizorama nghing te hi a lehlam zawng tak chuan kan vannei ti ta mai ila, Mizorama zawl kan neih lai deuh lama nghing a nih avang hian a pawi khawih pawh a lian tham lutuk rih lo a ni. Chuvangin, lei chet dan (ground motion) hi eng emaw chin chu a hrilhlawk (predict) theihin, kan leilung a lir lo nghing tawhte nat dan (amplitude) a zir khan kan in sakna tur hmunte leh kan hmun ngaih pawimawhte chu engzatin nge a lei a chet theih dawn tih a ngaihruat theih a ni. 

Mithiamte chhut danin lirnghing thlenna hmun (epicenter) aṭanga kilometer 350 thlengah hian chhiatna thleng thei turin an ngai a ni.

Engnge fault chu?

Civil Engineering thlirna aṭanga a pawimawh chin sawi ta ila, a chhan chu, mihringte tual châina (built-up environ-ment) china kan inthlurbing (concentrate) vangin. Fault chu, lei chhung rila lei leh lei inzawmna a dik lo lai, lei chhung khi chat sawina a ni mai a. Fault hi a len dan a zirin mi thiamten a maximum magnitude tur chhut dan an siam chhuak leh a, chumi hmang chuan a magnitude sang ber tur kha fault tan khan a rawn ngaihruat (predict) leh theih ta a ni. 

Tun thleng hian lirnghing zirna lama sang em em America leh Japan-te pawh zaa za in tuman an la ringlawk thei lo a ni. Awlsam deuha sawifiah dawn chuan - chaw chhumna cooker hi, a phit tawp ngai lo a, a si sér sér a, a rawn phit thut ang hian, fault reng reng hi, a rawn tipuaktu source hian, a hmain magnitude té reuh té té, mihringin kan hriat mai theih loh, lirnghing tehna (seismograph)-in a hriat theih hi a lo tichhuak (release) fo tawh ṭhina rin a ni. 

Seismic Hazard

Lirnghing vanga chhiatna lo thlengte hi Seismic Hazards an ti a, lirnghing vanga chhiatna tih te pawn a sawi theih ang. Chu mi chuan kan In, lei (bridge), tuikhuah, lung rem, leimin leh thil hrang hranga lirnghing vanga chhiatnate a huam vek a ni. Lirnghing vanga chhiatna laka kan in leh lo, lung rem (retaining wall), lei (bridge) dawh hrang hrangte an him theih nan Earthquake Resistant Design of Structures hmangin kan siam (design) thei a ni. Chuta pawimawh hmasa ber chu ground motion kan sawi tak kha a ni. Zaa za ring dik thei lo mah ila, leilung chet dan tur kha kan hisap (estimate) dawn a ni, kan in sakna turah khan chu mi hmang chuan kan in chu kan design tur a ni. 

Ground motion (lei che) sang thei bera rin (Maximum Credible Earthquake MCE) hmangin - Nuclear Power Plant anga thil chhiat hlauh­awm te hi design ṭhin a ni. MCE hi lirnghing tehnaa a sang thei ang ber leh na ber, khami hmunin a tuar theih tawk kha tihna a ni a, a magnitude lam ni lovin a lei chet dan kan tih ‘Ground motion’ khan a hril dawn a ni. Heng MCE-te hi khami zata sang lei che tur khan khami lirnghing kha kum ~2500 dan vela lo let leh 

ṭhina ngaih an ni. 

MCE-in a huam bak chu Design Basis Earthquake (DBE) an ti a, DBE hmanga in kan sak hote chu lei chet dan kha kum ~475 dan vela lo let leh tura ngaihruat a ni thung. Vanneihthlak takin, lehkhabu (code) hman tur hi Bureau of Indian Standards (IS1893) hian min siamsak hlauh a, keimahnin kan zawn chhuah theih kher loh pawn hemi hman hi a him tawk tura ngaih a ni. 

ERDS pawimawhna

Earthquake Resistant Design of Structures (ERDS)-in a ngaih pawimawh ber chu, kan in sak, kan thil sak reng reng a tlu rup tur a ni lo; muangchangin a kul phawt ang a, mihring in saseng hmanin a awm tur a ni, tih hi a ni. Engatinge MCE vekin kan inte hi kan design mai loh tih zawhna a awm mai thei, a chhanna chu - lirnghing na lutuk hi chu kan dam chhungin a lo kal kher lo thei, mahse a tawrh tawk vel (mid range) neuh neuh Mw 4.0-7.0 velte chu tawng zeuh zeuh tura rin niin a lo let leh hun tura ngaihruat pawh kum ~475 (DBE) vela ni a, chuvangin chhe thiang lo - Nuclear Power Plant velte a nih loh chuan DBE in design ṭhin a ni. 

In chim thut lo tur hian pawimawh hrang hrang a awm a, Earthquake Resistant Design of Structures chuan building hnuai ber aṭanga chhung ber rih dan inang chho vekte hi a ngai pawimawh a, in kan sakin a theih chin chinah buiding hnuai ber aṭanga chung ber thlengin a inchawih tawk (symmetric) a sak tur a ni. 

In chhawng hnuai lam âwl te hi ERDS chuan a duh lo em em a, hemi sak loh in hnuaiah hian a load kha tling khawmin a che dawn a ni. Gangtok earthquake kan sawi takah pawh khan chutiang chu hmuh tur a awm a ni. 

Chhawng tam tak, lehlam zang lehlam ritte hi ṭha a ti lo a ni. Pipu kan uai a, a sir téah kan ṭhu a, a hrui a vir ta ṭhin ang khan kan in kha a vir ve chuai chuai mai dawn a ni. Chutih rualin, loh theih loha khami floor kha kan ping phui thei dawn lova a awl dawn a nih chuan a ban kan tichak/tirinawm mai tur a ni. A chung chhawng rihna chu a hnuai awl rihna aiin 30% bakin a chak zawk tur a ni lo. Ban reng reng hi beam aiin a chak ngei ngei tur a ni. A chhan chu beam kha a chhiat chuan in pumin a tuar dawn lo, mahse ban pakhat lek chhia hian in pum a khawih buai thei thung. 

Ban tawi bik, floor dang aia tawite pawh hi an chhe hma duh em em bawk. Kan rama in kan sak dan, thlang lama kan beam lawr, bang awm lo, chhak lam lei ring angte hi a thlang lamah hian shear wall (bang brick chauh a siam ni lo, RCC a siam) emaw siam ngei ṭhin ila. 

Mizorama kan ngaih­pawimawh em em ngai chu kan in rah chhan hi a ni. Kan duh duhin leite hi kan lai ringawt zel a, lei reng reng hian chak chin an nei vek a, khami aia tama kan nek chuan lei kha a lo chim ta mai ṭhin a ni. Chuvangin, in sa tur reng reng chuan kan in sakna hmun tur hi a bearing capacity kan mithiamte hi lak tir ṭhin i la, thui takin kum 10/20 hnua kan in tawlhte hi kan titlem thei ang. 

Chumi piahah kopanga in sa tur tan, mahnia lei lai ve ngawt loin kan lei laih tur kha mi thiamte rawn chungin a hmun a zirin test pangngai tak tih hnuah chauh lai tawh ṭhin ang u. Kan lei laih khan eng zata chakna (strength) nge a neih tihte kan hriat chuan kan laih dan tur leh kan sak dan tur chenin min pui thei a ni. 

Khâmpanga in sate hian sir zawnga leiin bang a nekna (lateral earth pressure)-te hi kan ngaihtuah tel ngai em? Kan bang, khampanga mi kha retaining wall kan tih mai angin a chhaka lei a nek a, lei khan a theih tawkin a nek let ve bawk a, hei vang hian retaining wall pawh a chim fo reng a ni. Chuvangin, Lateral Earth Pressure hi ngaihthah chi a ni lo. Mahse, lateral earth pressure hre tur chuan a lei kha i test leh tho a ngai a ni. 

Lei test tur hian hmun hrang hrangah a tih theih. Mizoram University-a Civil Engineering Department-ah te, PWD Quality Control-ah te leh Geologist hrang hrangten an test thei bawk a ni. Kan in sak dawna kan ngaihtuah ve theih tur ṭhenkhat, kan in a lo ṭhat zawk nan man tlawm te te han sawi ila: Kan lei laih te bung vuta lai loin, a chhawrdawh zawnga laih hi a thlanawm viau. Sang taka lei kan lai a nih chuan soil nailing (lei kilh) hi tih ngei ngei bawk tur a ni. 

Kan in foundation rahchhan tur ban thlang leh chhak te 45o aia insan hleih loa ruahmanna siam hram hram tum ila. Leilung pian hmang tihchhiat loh hram nise, 60o aia awihah phei chuan fimkhur leh zuala ruahmanna siam a ngai tawh a ni. Sak loh mai pawh duhthusam zawk a ni. 

Ring rod hook-te hi kual ṭha deuhin, 135o vela tih kawm ni thei se. Beam tih len duh vanga ban zawna thir elh kual ai chuan ban tih len zawk mai nise. Brick bawk thum dan zelah rod sut te deuh phum tel ni thei se. Lintel beam ṭha taka siam ni thei se. Beam thlawk chhuak pumpelh hram theih nise. Beam leh slab te chhun rual ṭhin nise. Leihlawn (staircase) dahnate kan building sak nen a inzawm loha siam theih nise. A awmzia chu ban hran neia ruahman tur a ni. 

Beam pheiah ban duh duhna laia ṭo tir ringawt te hi tih loh tur a ni. Foundation, ban, beam leh slab-ah te cover block chak tak hman tur a ni. In chungah tui khuah fix a siam loh nise. Foundation hnuaia balu dah te hian eng emaw chen a veng ve a ngaih a ni.