IonosphereicfoF2variationsareverysensitivetotheseismiceffectandresultsofionosphericperturbationsassociatedwithearthquakesseemtoveryhopefulforshort-termearthquakeprediction.OnJanuary18,2011at20:23UTagreatearthquake(M=7.2)occurredinDalbandin(28.73°N,63.92°E),Pakistan.Inthisstudy,wehavetriedtofindoutthefeaturesofpre-earthquakeionosphericanomaliesbyusingthehourlydaytime(08.00a.m.-05.00p.m.)dataofcriticalfrequency(foF2)obtainedbythreeverticalsoundingstationsinstalledinIslamabad(33.78°N,73.06°E),Multan(32.26°N,71.51°E)andKarachi(24.89°N,67.02°E),Pakistan.TheresultsshowthesignificantanomaliesoffoF2intheearthquakepreparationzoneseveraldayspriortotheDalbandinearthquake.ItisalsoobservedthattheamplitudeandfrequencyoffoF2anomaliesaremoreprominentattheneareststationtotheepicenterascomparedtothosestationsneartheoutermarginoftheearthquakepreparationzone.TheconfidencelevelforionosphericanomaliesregardingtheseismicsignaturescanbeenhancedbyaddingtheanalysisofsomeotherionospheicparametersalongwithcriticalfrequencyofthelayerF2.
