gin.left + ',' +
            margin.top + ')');

    var x = d3.time.scale()
        .range([0, width])
        .domain(timeExtent);

    var brush = d3.svg.brush()
        .x(x)
        .on('brushend', brushend);

    context.selectAll('circle.quake')
        .data(data.features)
        .enter()
        .append('circle')
        .attr('transform', function(d) {
            return 'translate(' + [x(new Date(d.properties.time)), height / 2] + ')';
        })
        .attr('r', pointRadius)
        .attr('op