Both the events B1 and B2 are associated with InterRAT measurement reporting configuration.
B2-UTRA (-72, -76) are telling about event B2 threshold 1 and threshold2 values respectively.
Since threshold1 represents ThresholdEUTRA which will be a RSRP value while threshold2 represents ThresholdUTRA which will be utra-RSCP ( Received Signal code power).
Please go through the following information which will help you to understand.
ReportConfigInterRAT ::= SEQUENCE {
triggerType CHOICE {
event SEQUENCE {
eventId CHOICE {
eventB1 SEQUENCE {
b1-Threshold CHOICE {
b1-ThresholdUTRA ThresholdUTRA,
b1-ThresholdGERAN ThresholdGERAN,
b1-ThresholdCDMA2000 ThresholdCDMA2000
}
},
eventB2 SEQUENCE {
b2-Threshold1 ThresholdEUTRA,
b2-Threshold2 CHOICE {
b2-Threshold2UTRA ThresholdUTRA,
b2-Threshold2GERAN ThresholdGERAN,
b2-Threshold2CDMA2000 ThresholdCDMA2000
}
},
...
},
hysteresis Hysteresis,
timeToTrigger TimeToTrigger
},
periodical SEQUENCE {
purpose ENUMERATED {
reportStrongestCells,
reportStrongestCellsForSON,
reportCGI}
}
},
maxReportCells INTEGER (1..maxCellReport),
reportInterval ReportInterval,
reportAmount ENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity},
...,
[[ si-RequestForHO-r9 ENUMERATED {setup} OPTIONAL -- Cond reportCGI
]],
[[ reportQuantityUTRA-FDD-r10 ENUMERATED {both} OPTIONAL -- Need OR
]],
[[ includeLocationInfo-r11 BOOLEAN OPTIONAL -- Need ON
]]
}
ThresholdUTRA ::= CHOICE{
utra-RSCP INTEGER (-5..91),
utra-EcN0 INTEGER (0..49)
}