Earthquake Clusters

<!--
  说明：地震点聚合
  核心逻辑：Cluster 源的 features 属性取簇内数量与最大震级，样式按数量放大
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>地震点聚合</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:12px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  #info{margin-left:auto}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label><input type="checkbox" id="agg" checked> 聚合</label>
  <span>400 个震中 · 震级 2.0 至 6.5</span>
  <span id="info">—</span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var fromLonLat = ol.proj.fromLonLat;

  var rawSource = new ol.source.Vector();
  var feats = [];
  for (var i = 0; i < 400; i++) {
    var lon = 100 + Math.random() * 22;
    var lat = 24 + Math.random() * 16;
    var mag = 2 + Math.random() * 4.5;
    var f = new ol.Feature({ geometry: new ol.geom.Point(fromLonLat([lon, lat])) });
    f.set('mag', Math.round(mag * 10) / 10);
    feats.push(f);
  }
  rawSource.addFeatures(feats);

  var clusterSource = new ol.source.Cluster({
    distance: 42,
    minDistance: 16,
    source: rawSource
  });

  function magColor(mag) {
    if (mag >= 5.5) return 'rgba(200,40,28,0.90)';
    if (mag >= 4.5) return 'rgba(226,110,40,0.88)';
    if (mag >= 3.5) return 'rgba(214,170,50,0.88)';
    return 'rgba(40,120,220,0.86)';
  }

  function clusterStyle(feature) {
    var members = feature.get('features');
    var size = members.length;
    var maxMag = 0;
    members.forEach(function (f) { maxMag = Math.max(maxMag, f.get('mag')); });

    var radius = Math.min(7 + Math.log2(size + 1) * 3.5, 26);
    return new ol.style.Style({
      image: new ol.style.Circle({
        radius: radius,
        fill: new ol.style.Fill({ color: magColor(maxMag) }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 2 })
      }),
      text: new ol.style.Text({
        text: size > 1 ? String(size) : '',
        font: '600 11px sans-serif',
        fill: new ol.style.Fill({ color: '#ffffff' })
      })
    });
  }

  function pointStyle(feature) {
    var mag = feature.get('mag');
    return new ol.style.Style({
      image: new ol.style.Circle({
        radius: 3 + mag * 1.5,
        fill: new ol.style.Fill({ color: magColor(mag) }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 1.2 })
      })
    });
  }

  var clusterLayer = new ol.layer.Vector({ source: clusterSource, style: clusterStyle });

  var view = new ol.View({ center: fromLonLat([111, 32]), zoom: 4, minZoom: 2, maxZoom: 19 });

  var map = new ol.Map({
    target: 'map',
    layers: [new ol.layer.Tile({ source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}) }), clusterLayer],
    view: view,
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  var info = document.getElementById('info');

  document.getElementById('agg').addEventListener('change', function () {
    map.removeLayer(clusterLayer);
    clusterLayer = this.checked
      ? new ol.layer.Vector({ source: clusterSource, style: clusterStyle })
      : new ol.layer.Vector({ source: rawSource, style: pointStyle });
    map.addLayer(clusterLayer);
    info.textContent = this.checked ? '聚合显示' : '原始震中显示';
  });

  info.textContent = '聚合显示';
})();
</script>
</body>
</html>