<select id="target_menu" name="sort_by">
    <option selected="selected" id="position" value="0">varsayılan</option>
    <option id="sec1" value="1">secenek1</option>
    <option id="sec2" value="2">secenek2</option>
    <option id="sec3" value="3">secenek3</option>
    <option id="sec4" value="4">secenek4</option>
</select>

<button class="buton">
    Button1
</button>

$(function(){
    $('.buton').click(function(){
    
            if ($('#target_menu').val() == 0) {
        var aranan= $('#sec4').attr('value');
        $('#target_menu').val(aranan).trigger('change');
        }
    });
})