$(document).ready(function () {
    $('#alerta thead th').each(function () {
        var title = $(this).text();
        $(this).html(title + ' <input type="text"/>');
    });

    var table = $('#alerta').DataTable();

    table.columns().every(function () {
        var table = this;
        $('input', this.header()).on('keyup change', function () {
            if (table.search() !== this.value) {
                table.search(this.value).draw();
            }
        });
    });
});