To determine which scenario best demonstrates proactive workplace safety behavior, we need to review each option and identify the one that aligns with the principles of proactive safety management.

1. Waiting for a supervisor to notice hazards: This option describes a passive approach where employees rely on their supervisors to identify safety issues. This is not proactive because it does not involve taking initiative to address safety concerns before they become problems.
2. Reporting hazards after incidents happen: Although reporting is crucial, waiting until after an incident occurs before taking action is reactive rather than proactive. Proactive behavior would involve taking steps to prevent incidents from occurring in the first place.
3. Identifying and correcting hazards before accidents occur: This scenario involves actively looking for potential hazards and taking corrective actions before any accident occurs. It embodies the essence of proactive behavior, which is to anticipate and mitigate risks ahead of time.
4. Discussing only past safety problems in meetings: Focusing solely on past safety issues without addressing current or potential future risks is a reactive approach. Proactive safety management would also include planning to prevent future incidents.

The correct answer is therefore:

Identifying and correcting hazards before accidents occur

By evaluating each option, we see that the third option demonstrates a proactive approach to workplace safety by preventing risks and ensuring a safer working environment.