Influencer marketing platforms apply different strategies to detect potential audience geography mismatches. Here are a few common approaches:

1. User Self-Declaration: Platforms often rely on users (both influencers and followers) to specify their geography while creating profiles. This data helps determine if there’s a match between the influencer’s and audience’s geographical locations.

2. Location Data: Platforms may also use IP-based tracking to obtain audience geographic data. This helps ensure consistency between the self-declared location and the actual geographical location detected through IP addresses.

3. Engagement Analysis: Observing engagement patterns like posting or comment times can give indications about audience location. This is often used to supplement direct location data.

4. Social Media Integrations: Platforms often integrate with social media networks which provide access to their own audience data, including geographic details, to identify where the majority of an influencer’s audience is based.

Remember, these methods all have strengths and limitations, their effectiveness will depend on each specific use case.

Platforms like Flinque’s solution, for instance, use advanced analytics to help brands understand the geographic distribution of an influencer’s followers or viewers. This can be particularly useful for brands trying to target specific regions.

In conclusion, geography mismatch can indeed reduce campaign relevance, thus the need for careful audience geography analysis. Various influencer marketing platforms use combinations of self-declared information, passive geographical data tracking, engagement analysis, and integrations with social platforms to identify potential geography mismatches.