银行卡为什么被冻结？这个问题涉及到多个可能的原因，以下是基于这个问题的解析以及英文翻译对照：

首先，银行卡被冻结可能是由于账户出现异常交易。当银行监测到异常交易时，例如：短时间内多次进行大量交易、不同地点进行大额交易、进行非正常交易时间（如非营业时间）的交易等，银行为了防止诈骗或洗钱等犯罪行为，会暂时冻结账户。等到持卡人或者相关方解释清楚或者提供必要的证明材料后，银行会解除冻结。英文翻译为: Why is my bank card frozen? This question involves multiple possible reasons. The following are the reasons and their English translations:

Firstly, bank cards may be frozen due to abnormal transactions. When the bank detects abnormal transactions, such as multiple transactions within a short period of time, large transactions from different locations, or transactions made during non-business hours, the bank may temporarily freeze the account to prevent fraud or money laundering. The bank will unfreeze the account after the cardholder or relevant parties provide sufficient explanations or necessary proof materials.

其次，银行卡被冻结可能是由于账户长时间无活动。如果银行卡长期不使用，银行会视为无价值账户，从而采取冻结措施以防止资源浪费。如果持卡人想要解冻，可以携带本人身份证到银行柜台进行咨询或解冻操作。英文翻译为: Secondly, bank cards may be frozen due to long-term inactive accounts. If bank cards are not used for a long time, the bank may view them as dormant accounts and take freezing measures to prevent resource waste. If the cardholder wants to unfreeze the account, they can bring their ID to the bank for consultation or unfreezing operations.