Sct TRACON controller reported missing an A320 altitude read back; resulting in an MVA violation.

Attributes
ACN	1549107
Time
Date	201806
Local Time Of Day	0001-0600
Place
Locale Reference	SCT.TRACON
State Reference	CA
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Airspace Violation All Types Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Narrative:

I issued aircraft X a descent to [FL0]50 [MSL] in a [FL0]50 [MSL] MVA. Aircraft X read back [FL0]40 [MSL] and I missed it. When I observed aircraft X at [FL0]47 [MSL]; I issued a low altitude alert and climbed them back to [FL0]50 [MSL]. Aircraft X got down to [FL0]43 [MSL] before climbing back up.I need to pay attention to the read-back more carefully.

Original NASA ASRS Text

Title: SCT TRACON Controller reported missing an A320 altitude read back; resulting in an MVA violation.

Narrative: I issued Aircraft X a descent to [FL0]50 [MSL] in a [FL0]50 [MSL] MVA. Aircraft X read back [FL0]40 [MSL] and I missed it. When I observed Aircraft X at [FL0]47 [MSL]; I issued a low altitude alert and climbed them back to [FL0]50 [MSL]. Aircraft X got down to [FL0]43 [MSL] before climbing back up.I need to pay attention to the read-back more carefully.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.