Quieten Emergency Alerts On iPhone As They Happen
An emergency alert is issued by the government of any country that supports them. It is possible to opt out of these, apart from certain regions such as Canada. However, for those that have them enabled, they may want to mute the alarm while they are reading the important information brought by the alert.
Please note that this will not mute future alerts. It will only mute the ongoing one once it has been received by an iPhone. The noise will still sound initially.
When you receive an emergency alert, an alarm-like noise will sound and a notification will appear that informs the user of the emergency. After a certain amount of time, the alarm will stop.
To mute it instantly, just press the 'volume down' button. This will stop the alarm but still show the notification.
You can then dismiss the notification once you have read it.
Related articles
About emergency and government alerts on iPhone - Apple Support
Notes:
This is my first User Tip. Any constructive criticism is appreciated. Please feel free to add on with any missing information.
Thank you, Encryptor5000, for adding on useful information to this User Tip! It has been edited accordingly.